16:38 Live scorecard
West Indies cruise to an emphatic nine-wicket victory as they chase down 59 in 12.2 overs.
Gayle finishes unbeaten on 37 from 36 balls, while Bravo made nine from 26 balls.
With this victory, West Indies jump to second in the standings in Group B with four points from three matches, with a net run rate of +2.667.
Benn was the star of the show for the visitors as he took four for 18 to bowl out Bangladesh for a paltry 58.
"I thought we were really poor with the bat. Hopefully we will come back strongly," says Bangladesh Shakib after the match.
West Indies pacer Kemar Roach is named the man of the match for his splendid bowling.
16:17 Live scorecard
Darren Bravo gets his first boundary as he cuts a short ball from new bowler Ashraful through the covers.
Bravo gets a single off the last ball of the over as he hits one to the long-off fielder.
He is content to play the waiting game as he sees out another three balls from Naeem in the next over, before taking a single off the next. Gayle also gets a single in that over as West Indies look to cruise to their target.
Meanwhile, the crowds have started to pour out of the stadium. It's just two hours into the match and West Indies need a mere 10 runs for victory.
16:11 Live scorecard
Bangladesh introduce Abdur Razzaq into the attack, but he starts with a poor first over that sees him bowl two wides down the leg side.
Gayle continued his attacking approach as he charged down the wicket and clipped Razzaq through midwicket for a four.
Darren Bravo gets off the mark in the next over with a single through the covers off Naeem. Gayle chips down the wicket, but on realising that he is beaten in the flight, just defends it.
He ends the over in style as he chips Naeem down the ground for his fifth boundary, that takes him to 29 from 28 balls.
16:04 Live scorecard
Naeem Islam produces a rare moment of joy for Bangladesh. He manages to break through Smith's defences to bowl him for six.
Brian Lara-look alike Dwayne Bravo walks out to the middle. He offers the straight bat to the rest of the deliveries in that over to give Naeem a wicket maiden.
The pitch is ideal for spinners and Bangladesh must be ruing at not having posted a total close to the 200-run mark.
16:00 Live scorecard
Naeem Islam beats Gayle with a beauty. The off-spinner got one to turn and bounce a great deal, that also beat wicketkeeper Rahim, to get two byes for the West Indies.
Gayle looks to play it on the leg side but gets an inside edge to get two runs from the fine leg region.
Bangladesh make a bowling change, bringing in Rubel Hossain to replace Shafiul. Gayle charges down the wicket to Rubel but can get only a single.
A few deliveries later, Gayle chips Rubel down the ground but the ball stops on dropping, giving the left-hander another couple of runs.
Gayle seems in a rush. He charges down the wicket to Rubel and pulls a short ball over the mid-on fielder for his second four. The next ball is also despatched over that same fielder for another four to race to 21 from 19 balls.
15:51 Live scorecard
Bangladesh's 58 all out is the fourth lowest total in the history of the World Cup. It is also the lowest total by a Test playing nation in the World Cup.
Gayle makes them suffer further as he cracks a full delivery through the covers for the first four of the innings. His next drive through the covers is brilliantly saved by the fielder to keep him down for a single.
Devon Smith makes Shafiul pay for his error as he crashes a wide short delivery through the point region for his first four.
15:47 Live scorecard
It's spin from the other end as off-spinner Naeem Islam comes to bowl from the other end.
It's a pretty defensive field for a team defending just 59, with just a slip and leg slip in place.
Islam hits Gayle on the pads a couple of times but the ball looks to be sliding down the leg side and umpire Kumar Dharmasena rightly turns down both appeals.
Just one single from that over as Gayle plays one on the leg side.
15:44 Live scorecard
Devon Smith gets West Indies off the mark with a single on the leg side against Shafiul Islam.
Gayle also takes a single, through the covers, to get his first run and also bring up his 8000-runs in ODIs. It has taken the tall West Indies opener 226 matches to reach the landmark at an impressive average of 39.02.
Meanwhile, in another one-sided contest in the World Cup, New Zealand cruised to a ten-wicket victory
over Zimbabwe in Ahmedabad.
15:37 Live scorecard
It's one of the worst days in the history of Bangladesh cricket as their team folds up for a lowly 58 in 18.5 overs, their lowest total in ODIs.
Only Junaid Siddique (25) and Mohammad Ashraful (11) managed to score in double digits, while as many as four batsman are dismissed for ducks.
West Indies needed only three bowlers to finish off the hosts. Roach's pace was too hot to handle as he took three for 19 in six overs, while Sammy also used the new ball well to claim three for 21 in seven overs.
Benn was the best bowler among the three as he took four for 18 in 5.5 overs, including two maiden overs.
Bangladesh collapsed tamely as no batsman was willing to fight it out with all of them looking to play their shots when the need of the hour was to stay back and repair the early damage.
It would take more than a miracle for Bangladesh to bounce back from their horror show with the bat. A loss against the West Indies would be a big blow for their chances to make it to the quarter-finals.
15:32 Live scorecard
Bangladesh are bowled out for 58, their lowest total in One-Day Internationals.
Benn finishes off the innings with two wickets in his sixth over to finish with impressive figures of four for 18 in 5.5 overs.
Rubel Hossain was the final wicket to fall as Benn cleaned him up with his arm ball as the batsman was beaten for pace. A few deliveries earlier, Shafiul Islam hit one straight to Pollard at gully for a duck..it was like giving catching practice.
The crowd inside the stadium are angry and they are now throwing papers and whatever stuff they have in hand into the outfield.
15:25 Live scorecard
Good move from Sammy...getting back his premier fast bowler Roach to finish off things!
Roach obliges his captain immediately and picks a wicket with the first ball of his new spell.
Ashraful plays a reckless shot as he goes after wide delivery from Roach, only to edge it and is caught behind for 11.
Electing to bat first, Bangladesh might never dreamt of being reduced to 56 for eight in front of their home fans.
Roach looks unplayable at the moment and Bangladesh tailenders somehow managing to keep him out.
15:18 Live scorecard
The match seems headed for an early finish.
Benn continues to beat the batsman as he gets the ball to land in the right areas and turn a mile.
And soon, he gets his deserved wicket. Benn is rewarded for his persistence as he gets Naeem Islam to edge an outgoing delivery to be caught by wicketkeeper Thomas for one.
New batsman Shafiul Islam has no idea as Benn produces another magnificent delivery to spin past his outside edge. Wonder how long Bangladesh can last?
15:10 Live scorecard
Benn nearly picked up another in the 15th over.
He beat Ashraful with a flighted delivery that turned sharply past the outside edge. Wicketkeeper Thomas completed a sharp stumping, which was referred to the third umpire, but the decision went in favour of the batsman.
Benn beats Ashraful yet again as the ball turns and grips.
Ashraful brings some life back into the crowd as he cuts a short delivery from Sammy through point in the next over. This is the first four for Bangladesh after a long wait of 30 deliveries.
It's first drinks break and West Indies have dominated so far by claiming wickets at regular intervals.
15:04 Live scorecard
Bangladesh continue to play careless shots to give their wickets away.
Sammy bags his third wicket as Hasan chips one straight to Kieron Pollard at point to be dismissed for four. A real unnecessary shot given the situation as Hasan plays away from his body to give an easy catch to the point fielder.
15:00 Live scorecard
Bangladesh keep losing wickets and now find themselves in trouble after the wicket of Siddique.
Roach starts the over in erratic fashion as he bowls a no-ball but Bangladesh fail to make most of the free hit ball as Roach bowls a perfect yorker that Siddique can only dig out.
Another quick yorker gets the wicket of Siddique as he is struck right in front of the stumps to be trapped leg before wicket for 25.
They call for the review but it doesn't help as the replays confirm the ball struck him on the middle and leg stumps and looked set to hit the middle.
14:59 Live scorecard
Mohammad Ashraful, once regarded as Bangladesh's best batsman, is now struggling to keep his place in the team. He is not playing as a specialist batsman in this team but as an all-rounder, who is also expected to chip in with the ball.
Sammy continues to bowl to his field as he gives away just a single in his fifth over, while Benn is looking to test Ashraful and Raqibul Hasan with his flight.
The runs are proving hard to come for the hosts and the crowd are sitting quietly in their seats, hoping for a turnaround.
14:51 Live scorecard
Bangladesh continue to slip and now are reeling at 41 for five in the 11th over, following their dismissal of their captain Shakib.
The left-hander was caught in two minds as he first looked to play the sweep against Benn but then decided against it and looked to play straight. However, he ended up being caught up in two minds and missed a full delivery to be bowled for eight.
Mohammad Ashraful walks in at number 7. He is beaten off the very first delivery by Benn but sends the next ball crashing through the covers for a boundary.
14:45 Live scorecard
Shakib gets his first boundary as he slams Sammy through the covers off the second ball of the tenth over.
But Sammy sticks to a good line and length for the rest of the over to keep Bangladesh down to 40-4 after ten overs.
The two West Indies pacers have been excellent with the new ball. Sammy has claimed two for 13 in four overs, while Roach has two for 18 in five overs.
14:34 Live scorecard
Just three singles from the eighth over bowled by Sammy. Bangladesh look content to play the waiting game now, not willing to take risks after those early wickets.
In the day's other match between New Zealand and Zimbabwe, at Ahmedabad, the Kiwis are cruising at 80 without loss. That's in reply to Zimbabwe's 160 all out in 46.2 overs....(click for live scorecard
14:30 Live scorecard
Bangladesh's hopes now rest on their captain and their top player -- Shakib Al Hasan.
The left-hander is beaten by an outgoing delivery from Roach, but gets off the mark a couple of deliveries later with a double through square leg.
A fast yorker from Roach that Shakib does well to keep out and the next ball is played back to the bowler to end the over.
14:27 Live scorecard
Siddique brings the smile back to some extent as he chips Sammy over midwicket for a four.
The run rate is good, but Bangladesh have lost three big wickets.
Sammy then beats Siddique with a superb delivery, that swung miles to beat the left-hander all ends up.
14:23 Live scorecard
Sammy gets another wicket in his over.
Mushfiqur Rahim chips one straight to Ramnaresh Sarwan at short midwicket to be dismissed for a duck.
The home crowd are stunned into silence, they can't believe what they are seeing.
At the other end, Junaid Siddique has raced to 19 from 16 balls, with the help of three fours.
14:20 Live scorecard
West Indies captain Darren Sammy comes into the attack to replace Suleiman Benn, who bowled just one over.
And Sammy also strikes in his first over. Imrul Kayes, who made five, edges an outgoing delivery and is caught behind by wicketkeeper Thomas as Bangladesh slip for 16 for two after four overs.
14:18 Live scorecard
Kemar Roach strikes early!
He gets the big wicket of Tamim Iqbal, who went after a wide delivery only edge it and is caught by Darren Sammy at second slip for a duck.
14:17 Live scorecard
Bangladesh have won the toss and elected to bat against West Indies in the 19th match of the 2011 World Cup in Dhaka, on Friday.
The hosts went in with an unchanged team that beat Ireland, while West Indies also retain their team that beat the Netherlands.