Ulster made it four wins from four with a 22-17 victory at Glasgow Warriors which lifted them to the top of the Guinness PRO12 table.

Ulster dominated possession in the first half and led 15-7 at the break thanks to a try from centre Darren Cave, a penalty try and a penalty and conversion from Paddy Jackson.

Glasgow's points came courtesy of a Gordon Reid try converted by Finn Russell, on his return from the injury he suffered in last season's semi-final.

Ulster could have been even further ahead had they not had two scores chalked off by referee Ian Davies, who made repeated resort to video evidence.

A Russell penalty and a Tommy Seymour converted try put the Warriors into an unlikely lead, but a Jackson try at the other end, which he also converted to take his tally for the match to 12 points, condemned Glasgow to a second straight defeat.

Ulster went ahead after five minutes later thanks to a long-range penalty from Jackson.

Two minutes later full-back Jared Payne touched down by the posts, but a tip tackle by Ian Henderson on Seymour saw the try disallowed.

Cave finished off the game's first try after 16 minutes, but almost immediately Glasgow's only sustained attack of the half ended with prop Reid getting over from close range. Russell added the extras.

Hooker Rob Herring became the second Ulster player to have a try ruled out after going over in the 31st minute following a line-out drive.

But the visitors' luck turned right on half-time when referee Davies awarded them a penalty try and sent Glasgow winger Leonardo Sarto to the sin bin for a no-arms tackle on opposite number Charles Piutau.

Ulster introduced Ireland captain Rory Best for the first time this season seven minutes after the restart, but a Russell penalty got Glasgow within striking distance before full-back Stuart Hogg put in Seymour for his seventh try of the season, with Russell converting from touch.

However, it took only two minutes for Jackson to restore Ulster's lead with a try he converted himself.

In a frantic finish both sides had chances, but desperate defences ensured there were no more scores as Ulster's 100% start continued.