Rory O'Loughlin made it four tries in as many games as Leinster beat Ulster 22-7 in a Guinness PRO12 derby at the RDS.

Too many defensive lapses and turnovers saw Ulster fail to profit from a first half wind advantage, as a blistering sixth-minute try from Academy back O'Loughlin, coupled with Luke McGrath's score from a clever line-out move, had Leinster leading 17-0 at the interval.

Hayden Triggs' excellent performance up front typified the hosts' efficiency during the opening 50 minutes but after O'Loughlin completed his brace, Leinster's play became sloppy and their push for a bonus point try never materialised.

The increasingly influential Charles Piutau raided through for a deserved 76th-minute try for Ulster, who had been held scoreless while Leinster prop Jack McGrath was in the sin-bin.

Winger and man-of-the-match O'Loughlin lit up this New Year's Eve clash with a superb solo try, using line-out ball on halfway to burst in between Ruan Pienaar and Stuart McCloskey and then weave away from Andrew Trimble and Paul Marshall to score wide on the left.

Isa Nacewa's successful conversion was followed by Pienaar's second penalty miss, the South African unable to negotiate a tricky wind that was at Ulster's backs initially.

Nacewa punished a high tackle from McCloskey to make it 10-0 by the end of the first quarter, with Tommy Bowe uncharacteristically blundering from the restart as he fumbled a loose ball with the try-line in sight.

Showing seven changes from their 23-7 win over Connacht, Ulster had no points to show for a promising phase in the hosts' 22 via a strong scrum and counter ruck, while O'Loughlin did well to recover after his kick was half-charged down by Trimble.

Very good covering by Pienaar, who was playing at fly-half, closed off Sean O'Brien's opportunity to connect with O'Loughlin on a threatening Leinster break downfield - but Ulster's lacklustre defence, with 11 missed tackles in the first half an hour - gave way for a second try soon after.

Spotting that Trimble had moved infield to join the defensive line, Sean Cronin threw to the front of a line-out and Jack McGrath's quick transfer behind put scrum-half McGrath racing through a gap and over for Nacewa to crisply convert.

Leinster had their third try within two minutes of the resumption, Ross Byrne's dinked kick sitting up nicely for O'Loughlin to finish off by the left corner flag. Nacewa missed the difficult conversion at 22-0.

Ulster ended the third quarter in better shape and with 72 per cent possession, despite losing some key forwards - including captain Rob Herring - to injury. Chris Henry made a timely impact off the bench and pressure in the 22 from the visitors led to Jack McGrath seeing yellow for a ruck infringement.

Les Kiss' side threatened most through jinking full-back Piutau, however Leinster avoided a certain try thanks to Garry Ringrose's crucial tackle on Clive Ross.

Poor discipline meant Leinster continued to leak penalties and concede territory, allowing Ulster to open their account late on through Piutau who gobbled up Pienaar's inside pass to finish smartly for his third try in five PRO12 games.