Bath staged an impressive comeback to secure a bonus-point win over Ulster in a gripping Investec Champions Cup Pool 2 opener at the Rec.

But Bath quickly regained the lead after the restart through Tom Dunn and dominated the second half.

After Ulster's Matty Rea was sin-binned, Thomas du Toit, Cokanasiga and Matt Gallagher helped Bath pull clear.

While Ulster enjoyed a fruitful end to the first half when Burns and Doak struck in the space of four minutes, Bath thoroughly deserved the victory having held the Irish province scoreless during a dominant second-half display.

It is a third defeat in a row in all competitions for Ulster, who host Racing 92 in their second pool game in Belfast next week, while Bath travel to Cardiff, who were hammered by Toulouse on Saturday.

Ulster came into the game on the back of successive United Rugby Championship losses to Glasgow and Edinburgh, with head coach Dan McFarland criticising his side's training standards after the latter defeat.

And the Irish province's inaccuracy cost them during the early stages here, with Stewart Moore squandering a chance to send Robert Baloucoune clear and Nick Timoney doing likewise with Jacob Stockdale in space on the left.

But while Bath - for whom Scotland fly-half Finn Russell made his European debut - encountered line-out issues early on, they hit their stride when Cokanasiga finished in the corner after the hosts won a 5m scrum and Spencer slung a wonderful pass to the winger.

Ulster then had Baloucoune to thank for preventing a quick second Bath try, the wing racing back to dot down before Spencer could reach his own kick.

A Spencer penalty stretched Bath's lead, but having come through their most difficult period of the half, Ulster sprung into life when Ollie Lawrence kicked a clearance straight into Burns, allowing the Ulster fly-half to gather and touch down.

But if there was a touch of fortune about Ulster's first score, their second was the product of some wonderful rugby as Stuart McCloskey, James Hume and Baloucoune combined to send Doak away for the 21-year-old's second try in European competition.

Unfortunately for Ulster, they failed to build on their momentum as Bath quickly regained the lead in the second half, Dunn diving over after a powerful driving maul from a line-out.

Spencer's penalty put Bath 18-14 up before Ulster's chances were dealt a severe blow when South African prop Du Toit came off the bench to score Bath's third after Ulster replacement back row Rea was yellow carded for not rolling away.

From there, Bath were ruthless as Cokanasiga broke clear to secure the bonus point before Gallagher benefitted from slack Ulster defending to put the finishing touches on a satisfying afternoon for the 1998 winners.

'We came through a mental battle today'

Bath head coach Johann van Graan, speaking to TNT Sports: "We came through a mental battle today. First time this group has played in the Champions Cup, played very well for 35 minutes then conceded two soft tries.

"Then for us a group, it was a big moment in our season and the Champions Cup specifically. The thing that pleases me most was our positivity. I spoke beforehand about excitement and we struck through it."

Finn Russell, speaking to TNT Sports: "A better second half from us tonight, more clinical. We probably left four or five tries out there, especially in the first half.

"We could maybe put teams away earlier but overall, a bonus-point win, we're happy with that."

Line-ups

Bath: Gallagher; Cokanasiga, Redpath, Lawrence, Muir; Russell, Spencer (capt); Obano, Dunn, Stuart, Stooke, Ewels, Reid, Underhill, Barbeary.

Replacements: Annett, Schoeman, Du Toit, Van Velze, Coetzee, Schreuder, Bailey, Butt.

Ulster: S Moore, Baloucoune, Hume, McCloskey, Stockdale, Burns, Doak; Kitshoff, Stewart, O'Toole, O'Connor, Henderson (capt), Ewers, Timoney, McNabney.

Replacements:Herring, Warwick, M Moore, Treadwell, Rea, Cooney, Flannery, Lowry.

Referee: Pierre Brousset (Fra)

Sin-bin: Matty Rea (65)