A fifth Pro12 win on the bounce saw Glasgow Warriors close in on Ulster, while bottom two Treviso and Zebre were thrashed on Friday.
Glasgow Warriors picked up a fifth Pro12 win on the bounce to move level with an Ulster side who have now lost three of their last four.
Fresh from a fine victory over high-flying Leinster, the Scottish side produced a resilient display to overcome an early deficit and record a 27-17 triumph.
The Warriors found the first-half going tough on home soil, falling behind to a try from the returning Iain Henderson after only three minutes.
Finn Russell's hat-trick of penalties kept the deficit down to one point by the break, but a slow start to the second half saw Stuart McCloskey cross, with Paddy Jackson adding his second conversion to an earlier penalty on his 100th Ulster appearance.
Facing an uphill battle, the Warriors dug deep and ran in two tries in just three minutes through Stuart Hogg and Tommy Seymour.
Russell kept his cool to slot a 73rd-minute penalty and Hogg sent one sailing over from his own half with the last kick of the game to rob Ulster of a losing bonus point.
Elsewhere, bottom two Treviso and Zebre succumbed to heavy losses.
Treviso, propping up the table, were thrashed 56-8 by Cardiff Blues, while 11th-placed Zebre failed to score in a 47-0 reverse against Munster.