Shane Watson's allround brilliance powered Australia to an easy seven-wicket victory over Ireland in their opening Group B match of the Twenty20 World Cup yesterday.

Opening the bowling, Watson claimed three wickets for 26 runs and returned to hammer a 30-ball 51 as Australia chased down the 124-run victory target with 29 balls to spare.

Watson and his opening partner David Warner (26) put a brisk 60-run stand in the first seven overs to set the tone for what turned out to be a comfortable chase.

Australia lost their third wicket when Kevin O'Brien trapped Michael Hussey (10) in the 11th overs but Cameron White (22 not out) and captain George Bailey (six not out) stayed put to ensure an easy victory for the 2010 finalists.

Watson removed Irish captain William Porterfield with the first ball of the match and later broke a dangerous-looking fifth wicket partnership between the O'Brien brothers - Niall (20) and Kevin—both of whom fell to the blond Australian. "It wasn't as much a wicket-ball I suppose," Watson said referring to his first d elivery that dismissed the Irish captain. "But it just worked out luckily enough." "I t was a blueprint for this game and I am not exactly sure that is going to absolutely continue," he said on his role as a new ball bowler. "Depending on the teams, we will play in the conditions I suppose that could potentially change."

Watson was involved in the dismissal of the other Irish opener P aul Stirling (seven), catching him off fast bowler Mitchell Starc in the fourth over as Ireland lost their second wicket with 15 runs on the board. "Stirling is a quality hitter of the ball. So we knew that was a very important wicket, as well as (the wicket of) Kevin O'Brien," Watson said.

Ireland, having elected to bat first, never really recovered after losing their captain to the first ball and slumped to 33 for four wickets in 7.2 overs. Irish skipper Porterfield said they lost too may wickets in quick succession which denied them a bigger total. "If we had come up with an extra 40-45 runs it would have given us a chance," he said.

At one stage, even the 100-mark looked a distant possibility for Ireland but they still managed to post 123 for seven wickets largely because of the 52-run fifth wicket stand between the O'Brien brothers.

Kevin O'Brien was the top scorer for Ireland with 35 runs off 29 balls with five boundaries, while Niall scored 20 runs off 24 balls.