Australian cricketer Steve O'Keefe reacts after being dismissed during his team's defeat to Sri Lanka [AFP]

Ajantha Mendis became the only bowler to bag six wickets in a Twenty20 international as Sri Lanka clinched the series 2-0 against Australia with an eight-run win in the second match on Monday.

The unorthodox spinner finished with 6-16 off four overs as Australia lost their way after an explosive start provided by Shane Watson, who hammered a 24-ball 57 with five sixes and six fours.

Australia, who lost the first match by 35 runs, were eventually restricted to 149-9, after the hosts made 157 at the Pallekele International Stadium.

Sri Lanka were indebted to opener Mahela Jayawardene (86 off 63 balls) for posting a competitive total before Mendis ended Australia's early flourish.

Angelo Mathews also caught the eye for Sri Lanka with his key role in David Warner's dismissal off Mendis as he held a superb catch in the deep, but was about to step over the boundary line before relaying the ball to Jayawardene.

"That was a brilliant catch and the turning point," said Sri Lanka captain Tillakaratne Dilshan.

"This series is a big advantage going into the one-day and Test series."

Four for four

Watson dominated a 71-run stand for the opening wicket with Warner, but his dismissal in the sixth over triggered a collapse which saw Australia lose four wickets in the space of four runs.

"No excuses after the start Watson gave," said Australia skipper Cameron White.

"We just had to find a way but couldn't. Mendis bowled beautifully."

Sri Lanka were earlier strongly placed at 121-3 after 14 overs before paceman John Hastings rallied his team to eventually finish with 3-14 off four tight overs.

Fast bowler Brett Lee was the other main wicket-taker with 3-39, including two wickets in the last over.

Jayawardene dominated Australia's attack with exciting strokeplay, smashing one six and 12 fours in his sixth half-century in Twenty20 internationals.

He survived on 82 when he was caught off a Lee full-toss in the last over, but it was ruled a no-ball as it was above the waist. He fell in the same over, caught in the deep going for a big shot.

Sri Lanka, electing to bat after winning the toss, lost Dilshan in the third over before being steadied by Jayawardene.

Dilshan, who hit an unbeaten century in the opening match, contributed just four runs this time before being trapped leg-before by Lee.

Jayawardene then added 43 for the second wicket with Dinesh Chandimal (13) and 46 for the fourth with Kumar Sangakkara, who made a 16-ball 24.