Basseterre (St Kitts, Jan 18 (IANS): Aided by a patient half-century and a five-wicket haul from skipper Dunith Wellalage, Sri Lanka defeated Australia by four wickets in a Group D match of the Under-19 ICC Cricket World Cup here at the Conaree Sports Club on Tuesday (IST).

Wellalage first took five wickets for just 28 runs in his 10 overs and then returned when the chips were down to score a 71-ball 52 to keep Sri Lanka's winning record intact in the tournament. Sri Lanka are leading Group D with four points from two games, while host West Indies are second due to better net run rate (NRR) after a loss and a win.

Australia struggled to build partnerships having been put in to bat by Sri Lanka, their highest stand coming between Campbell Kellaway and Nivethan Radhakrishnan as they put on 46 for the fourth wicket. Kellaway was Australia's top scorer with 54 runs from 77 balls as the three-time champions slumped to 175 all out.

The last three wickets fell for just eight runs as 'Player of the Match' Wellalage produced his second double-wicket over of the match, as he also claimed his second five-for of the World Cup. This time the slow left-armer went for one more run than against Scotland to return figures of 5/28, which sees him five clear in the early race to top the wicket standings.

In reply, Sri Lanka kept above the required run rate but were consistently pegged back by the Australian quicks. Tom Whitney and William Salzmann took Sri Lanka's second and third wickets in the space of three deliveries to reduce them to 41 for three in their chase of 176.

Wellalage again helped to steady the ship, this time with the bat in hand, putting on a 70-run partnership with Anjala Bandara, before Bandara was dismissed sending an outside edge into the hands of wicketkeeper Tobias Snell. Wellalage continued on to his half-century, coming off 69 balls and featuring four fours and one six.

With Sri Lanka requiring just five runs, it seemed that Wellalage would steer the team home but he was dismissed caught and bowled by Whitney and it was left to Raveen De Silva to hit the winning runs as the Islanders emerged the only unbeaten team in Group D.

Brief scores: Australia 175 in 50 overs (Campbell Kellaway 54; Dunith Wellalage 5/28, Treveen Mathew 2/32) lost to Sri Lanka 177/6 in 37 overs (Dunith Wellalage 52, Anjala Bandara 33; Joshua Garner 2/21) by four wickets.