Leinster won a thrilling Irish derby against Munster, but even with the victory, Ulster moved into second place in PRO14's Conference B after their win on Friday night against Connacht.
Scarlets reamined top of Conference B at the end of the short block of six fixtures in the Guinness PRO14 before the focus turns to European Champions and Challenge Cup next week after defeating the Ospreys.
Southern Kings, one of two South Africans to join the competition this season, suffered their sixth straight defeat when losing to Benetton Treviso in Italy
LEINSTER 23 MUNSTER 17
Johnny Sexton set a new Leinster points-scoring record in a Guinness PRO14 victory over Munster at the Aviva Stadium.
Rory O'Loughlin's well-taken brace of tries had the hosts leading 14-7 at half-time, sandwiching an intercept score from Munster fly-half Ian Keatley.
An early second half penalty saw Sexton eclipse Felipe Contepomi's 1,225 points to become Leinster's record scorer, before the returning Keith Earls finished off a Tommy O'Donnell-inspired try for resilient Munster.
Two more penalties from man-of-the-match Sexton - taking his provincial career haul to 1,234 - sent the blue-clad hordes in the 46,374-strong crowd home happy, albeit that Earls' 78th-minute try bagged the reds a bonus point.
Both provinces were looking for a momentum-building performance heading into Europe next week, with Robbie Henshaw returning from the torn pectoral muscle which ended his Lions tour, and Earls making his seasonal debut.
BENETTON TREVISO 31 SOUTHERN KINGS 3
Angelo Esposito scored a try in each half as Treviso claimed a bonus point win over Southern Kings in the Guinness PRO14 match at Stadio Comunale Di Monigo on Saturday.
Wing Esposito's 31st minute score, along with three penalties from Marty Banks, gave the Italians a 14-3 lead at the break, with Marco Barbini and Cherif Traore crossing in the second half and Ian McKinley adding a conversion.
The Kings' only points of the game came from Pieter-Steyn de Wet's 38th-minute penalty.
Treviso were 9-0 ahead after 24 minutes thanks to Banks' boot, and the Kings were reduced to 14 men shortly after when Bobby de Wee was sent to the sin bin.
Esposito crossed to extend the lead but Banks' conversion attempt hit the post before De Wet missed a drop goal attempt. He slotted a penalty a minute later to cut Treviso's advantage to 11 points at half-time.
The second half was all Treviso, with tries from Barbini, Esposito and Traore sealing the bonus point as the Kings remained winless in Conference B.
OSPREYS 18 SCARLETS 19
Wales prop Samson Lee scored his first try in more than 100 appearances for Scarlets to edge the reigning Guinness PRO12 champions to victory over arch-rivals Ospreys.
Dan Biggar punished the stream of breakdown penalties awarded against the champions to keep the home side in the fight at Liberty Stadium.
But not even his perfect six from six was enough to haul them over the line in the end as Gareth Davies crossed twice for the visitors in an away success.
It meant a fifth successive PRO14 defeat for the four-time former champions to deepen their crisis and leave them anchored to the bottom of Conference A.
Victory for Scarlets took them back to the top of Conference B and put them in good heart ahead of their tough trip to Toulon in the European Champions Cup next weekend.