Ireland, a non-Test playing nation who also made it through the opening stage of the one-day World Cup in 2007, restricted Bangladesh to 137 for eight in their 20 overs at Trent Bridge.

"We didn't make anywhere near enough runs," Bangladesh's Australian coach Jamie Siddons told reporters. "The par score on that flat wicket was 170. The cooler heads prevailed and under pressure our guys weren't up to it."

Ireland reached 138 for four with 10 balls remaining following an aggressive exhibition of hitting from O'Brien. He struck four fours and two sixes after coming in with the match closely poised.

Man of the match Niall O'Brien, Kevin's brother, had laid the foundations for Ireland's victory with an innings of 40 from 25 balls, including three sixes.

"It's always nice to bat well when there are 10-15,000 people cheering you on," said Niall O'Brien.

"It doesn't feel like an upset to us as we came here expecting to beat Bangladesh and we have done it again."

Australian-born Trent Johnston earlier claimed three for 20 that helped to limit Bangladesh in their innings.

Bangladesh's total might have been even lower had it not been for the 20 runs that Mashrafe Mortaza struck from the last over, bowled by Alex Cusack.