Anthony Belleau spared Chris Ashton's blushes with a late try and subsequent conversion to help Toulon come from behind to beat Bath 24-20 in the European Champions Cup.

Toulon trailed 13-7 at the break of Sunday's (AEDT) Group 5 clash but was one-point ahead after Alby Mathewson crossed early in the second half.

However, Bath regained the lead just after the hour when Ashton miscued a kick from behind his own posts, the ball skewing off his foot and dropping to Jonathan Joseph, who had the easy task of touching down.

With four minutes remaining the Premiership side still led by three, but Belleau changed the outcome with a piece of individual skill to rescue a win, the replacement latching on to his own kick through to score, before adding the extras to wrap up victory.

The win maintains Toulon's perfect record after three games, while Scarlets closed to within three points of second-placed Bath with a 33-28 win of 14-man Treviso.

Racing 92 saw victory over Castres ripped out of their grasp in the final seven minutes in Group 4, Maama Vaipulu's try followed by a conversion and a penalty from Benjamin Urdapilleta snatching a 16-13 win.

There was nothing between the two sides in the opening 40 as Maxime Machenaud and Urdapilleta kicked two penalties apiece, but when Edwin Maka scored for Racing it looked like an away win.

Castres refused to lie down, though, to claim its first win in the competition, while Racing has lost two on the spin.

Munster leads the table after brushing aside Leicester Tigers at Thomond Park, Simon Zebo scoring one try and creating another as the Irish province recorded a 33-10 bonus-point victory.

Meanwhile, Ospreys condemned Northampton Saints to a third successive defeat in Group 2 as it clung on to a 43-32 victory despite being down to 13 men late on.

Twice Dan Evans crossed for the Welsh side as it surged into a 43-8 lead after an hour, Northampton's woeful form looking like suffering a humiliating home defeat.

The Saints threatened a comeback with four tries in eight minutes, but wiping out the deficit proved too much, even when Ospreys saw Rob McCusker sin binned and Hanno Dirksen sent off in the last 10.