Leinster and Munster tightened their grip on the top two Pro12 spots with dramatic respective victories over Ospreys and Glasgow Warriors on Saturday.
Leaders Leinster opened up a nine-point advantage over third-placed Ospreys with Ross Byrne's 79th-minute drop goal securing a 20-18 triumph at the Liberty Stadium.
Byrne's late three-pointer was not the end of the drama, though. Wales international Dan Biggar had an opportunity to win it for Ospreys with a penalty at the death, but he put it wide.
Munster kept pace with Leinster, but had to hold off a late fightback from the Warriors to win 10-7 at Irish Independent Park.
James Cronin crossed after just four minutes and a Rory Scannell penalty gave the Irish province a comfortable lead, but they had to defend doggedly after Finn Russell converted Stuart Hogg's try with 11 minutes remaining.
Scarlets capitalised on Ulster's 24-24 draw with Cardiff Blues on Friday by taking their place in the top four with a 51-5 thumping of Benetton Treviso, DTH van der Merwe scoring a hat-trick.
Having claimed just one victory in 17 league matches prior to last weekend, Zebre have now won two successive matches. The Italian side ran in four tries in a 29-14 triumph over fellow strugglers Newport Gwent Dragons.