Glasgow Warriors made it five wins from five
Keith Earls struck the decisive blow at Thomond Park as Munster ended a four-match losing run against rivals Leinster.
Ian Madigan and Ian Keatley traded blows with the boot, but it was Earls' first-half try - while Madigan sat in the sin-bin - that proved the difference between the two sides.
Leinster won an early penalty, after just three minutes when the hosts failed to release in the ruck, which Madigan kicked confidently from in front of the posts.
Munster flew back at the visitors in an unsurprisingly feisty opening, which led referee Romain Poite to fire an early disciplinary warning at Leinster skipper Jamie Heaslip.
Donnacha Ryan broke into the visitors' half after ten minutes but an efficient turnover, clearance and added pressure from Leinster forced Keatley into a rushed kick, straight into touch.
Munster's pack dominated the early exchanges and it earned a penalty and the opportunity for Keatley to draw them level, but his kick hit the post in the 14th minute.
Another electric Munster break saw Keith Earls offload to James Downey, who streaked into the opposition half but the visitors once again turned it over and eventually were awarded a penalty.
Madigan opted to go for the posts but his halfway-line effort fell narrowly short of doubling the Leinster lead.
But the visiting flyhalf didn't miss the opportunity for another three points after 24 minutes, sending his second penalty through the posts.
Six minutes later it was Keatley's turn to make amends, after further ill-discipline in the ruck, and he slotted a penalty from 35 yards to get the Munstermen on the board.
Keatley then made a streaking break from inside his own half before kicking a neat grubber, which was cut out well by Dave Kearney, but Madigan callously hacked the ball away and was sent to the sin bin for the remainder of the half.
From the resulting lineout Keatley sent a majestic cross-field kick to the right wing where Earls was waiting to collect and cross over on 33 minutes - Keatley duly converted.
Munster's enthusiasm didn't waiver but it cost them a series of penalties, the last of which came for Niall Ronan entering a maul from the side and Fergus McFadden deputised in Madigan's absence to pick up three points on the stroke of half time.
Munster kicked off the second half with another Keatley penalty, which he slotted from 40 yards, to make it 13-9 before Madigan returned to the pitch.
With a full compliment back on the pitch Leinster began to have a greater influence but a driven Munster backline kept them at bay - until Paul O'Connell was penalised for entering a maul from the side.
Madigan sent a very straightforward kick through the posts before a soft penalty on 55 minutes gave him the chance to restore Leinster's lead, which he did.
But Keatley re-took the lead for Munster just two minutes later, as this heated clash continued to produce plenty of penalties - he slotted another tricky one on 63 minutes to earn the hosts some breathing space.
Neither side showed any sign of taking a breather, as Lote Tuqiri and Rob Kearney each broke the Munster line but the hosts showed tremendous resolve.
Casey Laulala was next to make a line-breaking run but he was held up just short of the Leinster line - the Munstermen kept probing but Tuqiri led a breakaway to relieve some pressure.
Keatley missed the opportunity to put further daylight between the two sides three minutes from time, but it wouldn't prove costly as the Munstermen crept over the line
Pen: Keatley 4
Pens: Madigan 4, McFadden
Munster: 15 Felix Jones, 14 Keith Earls, 13 Casey Laulala, 12 James Downey, 11 Simon Zebo, 10 Ian Keatley, 9 Duncan Williams, 8 James Coughlan, 7 Niall Ronan, 6 Peter O'Mahony (captain), 5 Paul O'Connell, 4 Donnacha Ryan, 3 Stephen Archer, 2 Mike Sherry, 1 Dave Kilycoyne.
Replacements: 16 Damien Varley, 17 James Cronin, 18 BJ Botha, 19 Donncha O'Callaghan, 20 CJ Stander, 21 Conor Murray, 22 JJ Hanrahan, 23 Denis Hurley.
Leinster: 15 Rob Kearney, 14 Fergus McFadden, 13 Lote Tuqiri, 12 Gordon D'Arcy, 11 Dave Kearney, 10 Ian Madigan, 9 Eoin Reddan, 8 Jamie Heaslip (captain), 7 Sean O'Brien, 6 Kevin McLaughlin, 5 Devin Toner, 4 Mike McCarthy, 3 Mike Ross, 2 Sean Cronin, 1 Cian Healy.
Replacements: 16 Aaron Dundon, 17 Jack McGrath, 18 Martin Moore, 19 Rhys Ruddock, 20 Dominic Ryan, 21 Isaac Boss, 22 Jimmy Gopperth, 23 Luke Fitzgerald.
Referee: Romain Poite (FFR)
Glasgow Warriors 17-12 Scarlets
Glasgow Warriors made it five wins from five in the PRO12 as they beat the Scarlets 17-12 to move back to the top of the table.
Ryan Grant and Tim Swinson scored the tries that extended the Warriors' unbeaten start to the season to five games, ending the Welsh outfit's five-game run of victories against Scottish sides in the process.
Glasgow made a great start to the game as Fijian Niko Matawalu battered his way forward, and from a quick tap penalty the Warriors found themselves camped deep in the Scarlets 22.
Glasgow threw men into contact and Grant was driven over the line on four minutes, with the try awarded by the TMO. Duncan Weir added the extras to make it 7-0 as the Scarlets struggled to apply any attacking pressure to the visitors.
On 17 minutes Rhys Priestland did land a penalty for the home side to reduce the deficit, with play camped in the middle of the field as both teams strained for supremacy in the scrum.
A delightful step from the evergreen Sean Lamont put Glasgow back on the attack, with Swinson then driving deep into the Scarlets 22.
The ball was recycled and found its way to Swinson again who managed to squirm forward and get the ball down despite intense pressure from the Scarlets defence.
The TMO was again called on to judge the grounding but after a short pause the points were awarded and Weir added his second conversion of the evening.
Despite trailing 14-3 the Scarlets were having some success at the set-piece and after several scrum penalties Priestland stepped up to pop over a second penalty and send his side in eight points behind.
The Welsh international flyhalf opened the second half with another penalty and momentum was with the home side, who almost got their first try when Matawalu made a mess of the ball on his own line but redeemed himself with some desperate defending.
Glasgow lost Lamont to the sin bin for ten minutes for holding onto his man in the tackle as the Scarlets turned the screw without ever making the vital breakthrough.
The penalties kept coming, however, and with Priestland carrying a knock Jordan Williams took over the kicking duties and he made it a two-point game with 20 minutes still to play.
But just two minutes later Weir took aim from distance and popped over a long-range beauty to extend the Glasgow lead to five points as play went into the final quarter.
The Scarlets were unable to get the territory they needed to really apply pressure to Glasgow in the final minute with the Scottish side holding out relatively easily.
Weir was off target with a drop goal attempt that would have put the result beyond doubt, and with five minutes remaining Matawalu got himself sent to the sin bin for stamping at the ruck.
Williams took aim but his penalty effort never looked like finding the target and the Warriors saw out the final few minutes with 14 men to secure victory and move to the top of the table.
Pens: Priestland 3, J Williams
Tries: Grant, Swinson
Cons: Weir 2
Scarlets: 15 Liam Williams, 14 Nick Reynolds, 13 Jonathan Davies (captain), 12 Gareth Maule, 11 Jordan Williams, 10 Rhys Priestland, 9 Rhodri Williams, 8 Rob McCusker, 7 John Barclay, 6 Josh Turnbull, 5 John Snyman, 4 George Earle, 3 Jacobie AdriaanseSamson Lee, 2 Ken Owens, 1 Phil John.
Replacements: 16 Emyr Phillips, 17 Rob Evans, 18 Rhodri Jones, 19 Jake Ball, 20 Aaron Shingler, 21 Aled Davies, 22 Steve Shingler, 23 Adam Warren.
Glasgow Warriors: 15 Sean Maitland, 14 Niko Matawalu, 13 Niko Matawalu, 13 Mark Bennett, 12 Alex Dunbar, 11 Sean Lamont, 10 Duncan Weir, 9 Chris Cusiter, 8 Richie Vernon, 7 Chris Fusaro, 6 Robert Harley, 5 Al Kellock (captain), 4 Tim Swinson, 3 Moray Low, 2 Pat MacArthur, 1 Ryan Grant.
Replacements: 16 Fraser Brown, 17Jerry Yanuyanutawa, 18 on Welsh, 19 James Eddie, 20 Adam Ashe, 21 Scott Wight, 22 Gabriel Ascarate, 23 DTH van der Merwe.
Referee: Giuseppe Vivarini (FIR)
Assistant Referees: Chris Williams, Phil Fear (both WRU)
TMO: Tim Hayes (WRU)