Rhys Priestland's last-gasp penalty saw Scarlets snatch a dramatic 28-26 victory over bottom side Zebre at Stadio Sergio Lanfranchi.
Tommy Bowe's try double helped Ulster strengthen their grip on a semifinal spot as the visitors secured a 27-20 triumph over Connacht.
REPORT: Hat-trick hero Peter Horne fired Glasgow Warriors to an emphatic 36-17 victory over Cardiff Blues.
REPORT: Ospreys scored three tries in the final 15 minutes, to grab an unlikely bonus-point 33-13 win at Stadio Monigo.
Connacht have completed their internal review of the circumstances surrounding the questioning of Mils Muliaina in relation to an alleged sexual assault.
Sean Maitland has played his last game for the Glasgow Warriors and is facing a race against time to be fit in time for the World Cup.
Ulster have signed lock Peter Browne and scrumhalf Paul Rowley, both from London Welsh.
Leaders Glasgow Warriors open this round of Pro12 action by hosting Cardiff Blues at Scotstoun on Friday.
Ospreys hooker, and serving soldier, Matthew Dwyer has signed a new one-year deal at the Liberty Stadium.
Mils Muliaina faces an internal review from his Irish province Connacht, as he fights to clear his name of sexual assault allegations.