Ulster's fourth Magners League win saw them go top of the table after digging deep to see off the current Heineken Cup holders Leinster 16-14.

Three penalties and a conversion by Ian Humphreys from a second-half try from Isaac Boss saw Ulster home, though a late converted try from the last move of the game from substitute Luke Fitzgerald saw Leinster grab a valuable bonus point.

Ulster, who were without Paddy Wallace due to the Irish Rugby Football Union's player management programme and Stephen Ferris because of an ankle injury, played the conditions with far more intelligence than their star-studded opponents, who suffered their second league defeat.

Neither side managed to get the scoreboard ticking over until a late flurry of points at the end of the half.

A marvellous forward effort from Ulster - when they retained the ball for around 10 phases - resulted in Leinster hooker Bernard Jackman being sent to the bin after referee Andrew Small blew with the Leinster tryline open for Humphreys and Andrew Trimble.

Humphreys landed the penalty into the teeth of the gale but then, from the restart, Leinster turned the screw and, with Brian O'Driscoll pulling the strings, they surged towards Ulster's line in injury time.

Tamaiti Horua was binned for killing the ball, and Leinster ran the penalty with O'Driscoll putting Berne clear for the right corner. The Leinster outside half superbly converted and, suddenly, the visitors trooped off 7-3 in front.

With the conditions now behind Ulster, Humphreys narrowed the deficit with a second penalty five minutes after the resumption and then, three minutes later, Boss scooped a ball up from a ruck and broke down the blindside to run in from just short of 50 metres.

Humphreys made the tight angle conversion to give his side the lead 13-7 and was then just short with a penalty attempt from 55 metres.

All that remained was Humphreys' 73rd-minute strike which seemed to take it beyond the visitors, until that is Isa Nacewa's chip through for Fitzgerald, which Sexton then converted.