Leinster moved to the top of the RaboDirect PRO12 standings on Saturday by edging an absorbing 28-25 win against play-off rivals Glasgow Warriors.

Ian Madigan converted Rhys Ruddock's 63rd-minute try and kicked 13 points in all as Matt O'Connor's men took advantage of leaders Munster's defeat at the Scarlets. Returning to the RDS, where they lost to Leinster in last year's semi-finals, Glasgow gave their all in pursuit of only their second victory in 18 visits to Dublin.

Madigan accumulated 11 points and Noel Reid and man-of-the-match Darragh Fanning broke through for tries as Leinster took a 21-15 lead into half-time. Glasgow showed their attacking capabilities, with two Richie Vernon tries and an injury-time penalty from Finn Russell making it a six-point difference.

Niko Matawalu burrowed over from a ruck for the Warriors' third try with Russell's conversion putting them a point clear after 51 minutes. But Leinster's pack eventually broke the Scots' resistance, flanker Ruddock muscling over for the decisive seven-pointer on a wet night in the Irish capital.

Scarlets held on to claim a 18-13 victory over previous leaders Munster, who were denied an unprecedented clean sweep of victories over the four Welsh regions.

The Munstermen had to settle for a losing bonus point which stretched their lead to three points over Leinster. A try apiece from scrum-half Gareth Davies and flanker John Barclay were the backbone of the victory at Parc y Scarlets with Munster's only try coming from wing Gerhard van den Heever.

Kieran Marmion marked his 50th provincial cap with a try as Connacht ran out comfortable bonus-point winners in a 38-6 triumph over Benetton Treviso at the Sportsground.

Scrum-half Marmion's fifth try of the campaign came in a Connacht-dominated first half which ended 24-6 in their favour. Fionn Carr and John Muldoon also touched down before the break, and in a rain-lashed second period captain Muldoon scored once more from a successful lineout maul and returning number eight Eoin McKeon added a fifth try late on.

Cardiff Blues' miserable form continued on Saturday as they slumped to a 15-10 defeat at the hands of rock-bottom Zebre in Parma.

Cardiff had won just one of their previous eight matches in the tournament heading into the clash at the Stadio XXV Aprile, and it was to be another day of disappointment for the Welsh side as Zebre did the double over them in testing conditions. The Italians, whose 30-25 win at the Arms Park in round three was one of only two previous victories this season, took the lead after just three minutes when former New Zealand scrum-half Brendon Leonard crossed for a try that was converted by Kelly Haimona.

Zebre went in 12-3 up at half-time but Cardiff mounted a fightback, getting to within two points early in the second half when Tom Williams went over. But Italy's Luciano Orquera nailed a penalty to settle the nerves and the home side held on to condemn Cardiff to an 11th defeat of the season.

Two tries from Tommy Bowe on his comeback after three months out with a groin injury kept Ulster in third place as they racked up a bonus point 38-8 win over the overwhelmed Dragons.

Ulster scored five tries with Bowe's brace - he was substituted at half-time in a performance which must have impressed Ireland coach Joe Schmidt - being added to by scores from Ruan Pienaar, Sean Doyle and a penalty try, the latter which brought up the bonus point after only 32 minutes.

Paddy Jackson also put in a notable shift and kicked all five conversion attempts which will also have been noted by Schmidt, who may be without Jonathan Sexton for next week's Six Nations game against Italy. Ulster led 31-3 at half-time with their only try of the second half coming from Doyle as both sides tired after their five-day turnaround from their previous games.

Edinburgh broke their three-game losing streak with a gutsy 31-25 win over Ospreys at Meggetland. Although the visitors opened the scoring Edinburgh had built up a 22-11 lead by the break thanks to tries from Grayson Hart (2) and centre Sam Beard, with full-back Carl Bezuidenhout kicking two conversions and a penalty.

Jeff Hassler's second unconverted try for Ospreys cut Edinburgh's lead to three points but three second half penalties from Bezuidenhout saw them home. Although Ospreys stand-off Dan Biggar kicked five penalties, it could not prevent the top four hopefuls from slipping to defeat.