Jerry Flannery scored Munster's first-half try at Thomond Park
Munster (14) 22
Tries: Flannery, Carney
Pens: O'Gara 4
Scarlets (7) 13
Try: S Jones
Con: S Jones
Pens: S Jones 2
Munster stayed on course for the knockout stages of the Heineken Cup by ending Llanelli Scarlets' lingering hopes in a tough match at Thomond Park.
Jerry Flannery and Scarlets' Stephen Jones scored early tries at either end but three Ronan O'Gara penalties helped Munster lead 14-7 at the interval.
A Jones penalty cut Munster's lead to four and the Scarlets continued to look dangerous when the home side led 17-13.
But Brian Carney's 74th-minute try, after a turnover, made the game safe.
Munster produced early pressure and excellent ball-retention culminated in Flannery barging his way over the Scarlets line in the sixth minute.
O'Gara was forced to attempt a drop-kick for the conversion after the wind blew the ball off the tee.
However, the Scarlets were ahead by the 11th minute with Jones easily finding a gap in the Munster defence to touch down under the posts, after Mick O'Driscoll's errant pass had put the home side in trouble.
Wales and Lions fly-half Jones, whose penalty had come back off the woodwork and into O'Driscoll's hands, knocked over the conversion to put his team 7-5 ahead.
Ronan O'Gara had another solid game for Munster
O'Gara's 16th-minute penalty nudged Munster ahead again and O'Driscoll's line-out steal then helped set up an attack which yielded another three points for his fly-half.
Ben Broster's blatant ruck infringement gifted O'Gara another three points on 34 minutes and also sent the prop to the bin for 10 minutes.
Denis Leamy thought he had scored a Munster try in first-half injury time but the video referee ruled that the Ireland forward had been held up.
The play becamse increasing scrappy in the third quarter but Jones' 48th-minute penalty did cut the Munster lead to four points.
However, Munster were seven ahead again on the hour as O'Gara slotted his fourth penalty after Alix Popham had controversially been adjudged to have committed a high-tackle on the fly-half.
But the Scarlets continued to look dangerous and Morgan Stoddart's break put the Munster defence under huge pressure.
Indeed, the home side were probably relieved to concede only three points with Jones slotting his second penalty after an offside infringement.
Munster suffered a further blow on 66 minutes when prop Marcus Horan was sin-binned for throwing a punch in the scrum.
However, Munster's nerves were thoroughly eased when Carney ran in a try in the 74th minute after a turnover in the middle of the field.
To compound the Scarlets' woes, Alix Popham was immediately sin-binned for a high-tackle and while O'Gara missed the conversion, Munster were 22-13 ahead.
The Welsh side continued to battle but the job had already been done by Munster as they went back to the top of their Heineken Cup pool.
Munster coach Declan Kidney:
"The Scarlets kept the ball well in the first half but we made them work hard. It was a case of wearing them down in the first half and that helped us later on when we gained a few yards several times.
"I was worried at half-time though. Our dressing room at half-time was very subdued despite our lead. We managed to get three turnovers from their line-outs and that was a big boost.
"I'm not disappointed at not earning a bonus point. We got four and that was an extraordinary achievement. We can always improve and we will look at our performance.
"Clermont Auvergne will be a hell of a place to have to go to. But 10 days ago we might have had nothing to play for and these two wins have ensured we will have a great deal to play for next month."
Scarlets director of rugby Phil Davies:
"It was a very intense game and both sets of players went at each other with great tenacity. It was quite a good game from our point of view.
"I'm disappointed that we didn't win which we came to do. Inefficiency cost us at times. We were in the game all through and there were a few occasions in the second half when, if we kept the ball, we might have earned a penalty or a try.
"We want to win our last two games in the competition, certainly. I don't have a crystal ball to predict who will win the group. There are three fantastic sides left but we will play our part."
Munster: Payne; Carney, Tipoki, Mafi, Dowling; O'Gara, Stringer; Pucciariello, Flannery, Hayes, O'Callaghan, O'Driscoll, Leamy, Wallace, Foley.
Replacements: Horan for Pucciariello (52), D. Ryan for O'Driscoll (64). Not Used: Sheahan, Ronan, G. Hurley, Warwick, Lewis.
Sin Bin: Horan (66).
Llanelli Scarlets: Stoddart; M. Jones, King, J. Davies, Brew; S. Jones, Peel; I. Thomas, Hayter, Broster, Cooper, Eustace, Easterby, Bater, Popham.
Replacements: C. Thomas for M. Jones (49), Manu for Broster (59), MacLeod for Eustace (59), G. Thomas for Bater (59). Not Used: George, N. Thomas, Cattle.
Sin Bin: Broster (33), Popham (74).
Referee: David Pearson (RFU).