Tom Stewart scored a hat-trick as Ulster returned to United Rugby Championship action with a bonus-point win over play-off rivals Bulls.

Stewart restored Ulster’s advantage but the Bulls led 20-12 at half-time thanks to Zak Burger and Chris Smith.

Hooker Stewart completed his hat-trick and scrum-half Nathan Doak kicked nine points as Ulster ground out the win.

The victory at Kingspan Stadium meant Ulster have completed an unprecedented clean sweep over the South African sides – the Bulls, Stormers, Lions and Sharks.

It also put them in the perfect mood for their European Champions Cup quarter-final with Leinster in Dublin on Saturday.

In an enthralling first half, it took Ulster just three minutes to cross when neat hands through the backs allowed Michael Lowry to find returning wing Baloucoune, who had enough in the tank to race the length of the 22 and dive over in the corner.

Doak missed the conversion, and opposite number Smith also miscued from the tee with his first penalty attempt.

But the South African fly-half made amends with a long-range kick after Ulster were cut open by Burger, and James Hume was penalised for a high tackle.

After a couple of near misses, when Bulls handling let them down after some scything runs, it felt like a matter of time before they made Ulster pay.

And Jake White’s side got their reward midway through the half when Arendse rounded off a superb break.

A loose kick by Lowry gave Arendse space and he fed Canan Moodie, who collected his own chip, burst through the tackle of Stewart Moore and fed the ball to the Springbok full-back to score.

However, Ulster came again and Sam Carter was held up under the posts while his side had the penalty advantage.

But the hosts eventually capitalised when Stewart broke off a maul to drive over for his first try of the night and 11th of the season. Doak landed a superb conversion from the touchline.

In a half where most of the play was spent in the respective 22s, the Bulls went in ahead at the break as the power of their forward pack edged towards the line and Burger sniped in to capitalise on the stretched Ulster defence.

Smith converted and added a long-range penalty to give the Bulls an eight-point lead at the break.

But the game changed when Elrigh Louw was sent to the bin, a legacy of warnings from the first half for repeated infringements.

Stewart immediately pounced with his second score of the game from a maul.

Down to 14 players, the Bulls held out for the remaining nine minutes, but Stewart soon completed his hat-trick with a brilliant finish.

He was brought down shy of the line, but the 22-year-old managed to roll and touch down.

The Bulls came again and Smith’s penalty brought the margin down to three, but the ever-reliable boot of Doak restored Ulster’s six-point margin.

Knowing a converted try would snatch victory, the Bulls were ready to kick the ball into the Ulster corner after being awarded a penalty.

But referee Craig Evans reversed his initial decision when a replay showed replacement hooker Bismarck du Plessis had clattered Billy Burns in the build-up with an illegal tackle.

Dan McFarland’s men moved up to third in the table as replacement John Cooney kicked a penalty with the last action of the game.

Ulster: Lowry; Balocoune, Hume, Moore, Stockdale; Burns, Doak; Warwick, Stewart, Toomaga-Allen; Treadwell, Carter; McCann, Timoney, Vermeulen (capt).

Replacements: Andrew, O’Sullivan, Milasinovich, O’Connor, Sheridan, Marcus Rea, Cooney, Postlethwaite.

Bulls: Arendse; Moodie, Hendricks, Vorster, Kriel; Smith, Burger; Steenekamp, Grobbelaar, Smith; Vermaak, Nortje (capt); Van Staden, Brink, Louw.

Replacements: Matanzima, Du Plessis, Klopper, Swanepoel, Steenkamp, Papier, Steyn, Gans