Sri Lanka beat Australia by 20 runs at the Oval on Monday to reach the ICC Champions Trophy semi-finals.

- Scorecard

Earlier, Australia captain George Bailey won the toss and invited Sri Lanka to bat first in the Group A match.

Left-arm spinner Xavier Doherty struck in his fifth over as Sri Lanka opener Tillakaratne Dilshan (34) was caught by Shane Watson at first slip

Dilshan's 58-ball knock included just one boundary but he along with Lahiru Thirimanne added 72 runs (in 19 overs) for the third wicket to help Sri Lanka make good progress in the middle overs as they reached 92 for three after 23 overs.

Mitchell Johnson, who gave Australia an early breakthrough having Kusal Perera leg before wicket in the first over of the innings, came back for a new spell and got the wicket of Thirimanne (57), who was caught by Watson at midwicket.

Sri Lanka managed 36 runs in the Batting powerplay, while losing the wicket of captain Angelo Mathews.

A single off Johnson helped Mahela Jayawardene complete his 69th ODI fifty.

Jayawardene's 81-ball 84 not out helped Sri Lanka score a formidable 253 for eight in their stipulated 50 overs.

Nuwan Kulasekara struck in his very first over when he got the key wicket of Shane Watson, who was bowled off an inside edge for five.

The pacer also accounted for Phil Hughes, who was caught behind by wicketkeeper Kumar Sangakkara for 13 as Australia were reduced to 45 for two in the sixth over.

Glenn Maxwell blazed away to 32 off just 20 balls before being cleaned up by pace spearhead Lasith Malinga. He smashed five fours and a six during his breezy knock to lift Australia after a few early wickets.

More trouble was in store for Australia as they lost George Bailey thanks to a fine piece of fielding from Kulasekara whose flat throw from short fine leg caught the skipper well short of the crease.

Mitchell Marsh was then bowled by Angelo Mathews to make matters worse for the Aussies, who were left reeling at 80 for five in the 13th over.

Clint McKay and Xavier Doherty resisted for 75 balls, adding 41 runs for the last wicket to give Australia genuine hope of a victory before Tillakaratne Dilshan made the all-important breakthrough.

The part-time off-spinner took a brilliant one-handed catch to end a stubborn last-wicket partnership of 41 as Sri Lanka beat Australia by 20 runs.

The Australians still had more than seven overs to score the 21 runs they needed when McKay, on 30, scooped the ball firmly back towards the bowler who leaped to his left and clung on to a spectacular catch before being mobbed by his ecstatic team mates.

The Sri Lankans, who finished second behind England in Group A, will play Group B winners India in the last four in Cardiff on Thursday.

New Zealand were eliminated along with Australia from Group A.

England will face Group B runners-up South Africa in the first semi-final at the Oval on Wednesday.