Munster maintained their grasp on top spot in the Magners League as Ronan O’Gara’s 79th-minute penalty edged them over the finish line and dashed the Scarlets’ hopes of a first night success at their new home ground.

The Welsh region’s first league outing at Parc y Scarlets, their new £23 million Pemberton stadium, had a pre-match hitch as match referee Peter Allan from Scotland was delayed in a tailback, caused by a traffic accident on the M4.

Welsh official James Jones stepped in to take over the refereeing duties at what was the 31st different venue to stage a league match.

Shorn of the majority of their Welsh internationals, the Scarlets fielded a team with seven players under the age of 25. They included league debutants Matthew Jacob and Dominic Day.

But Munster, who were without the rested Paul O’Connell, John Hayes, Jerry Flannery and David Wallace, the injured Rua Tipoki and the suspended Alan Quinlan, made the better start.

They were 3-0 up within four minutes as stand-in captain Ronan O’Gara punished Vernon Cooper for a ruck offence.

The Scarlets began to settle in the intervening minutes, but after some decent continuity and a muscular burst forward from David Lyons, Rhys Priestland was off target from a right-sided penalty kick.

The hosts were beginning to find holes in the Munster defence. Skipper Simon Easterby managed to charge through a gap, only for the Scarlets to infringe on the deck and lose precious field position.

Munster came back strongly, working the ball through the hands and spreading the play left and right.

However, Nigel Davies’ men got back level on 21 minutes when Lifeimi Mafi was sin-binned for repeated ruck offences and Priestland knocked over the resulting penalty.

A scrappy period of play followed and both sides were guilty of some aimless kicking as they looked to establish a foothold in opposition territory.

Down to 14 men, Munster made sure they did not concede any more points and two tries in a seven-minute spell sent them in at half-time with a 15-3 lead.

The European champions engineered a fine try in the 31st minute. Mick O’Driscoll took a quick tap penalty and his well-weighted pass sent Niall Ronan hurtling towards the Scarlets 22.

Ronan offloaded for Ian Dowling and the winger, coming in from the left, shifted inside both Jacob and Morgan Stoddart to grab the game’s first try.

O’Gara missed the conversion and Stoddart, just minutes later, had to be alert to deny Dowling a second try as he chased down a kick into space from Tomas O’Leary.

But the Scarlets defence gave way again just before the break.

Munster managed to shove the home side off their own scrum ball, five metres from the Welsh whitewash, and with the set-piece invitingly to the left, number 8 Denis Leamy picked off the base and wrestled his way past two tacklers to score.

O’Gara converted but Munster were sluggish on the restart and Priestland cut the gap with a penalty, three minutes into the second half.

With Munster lacking cohesion, the Scarlets assumed control and counted themselves unfortunate to be called back for a forward pass when they sprung an excellent 51st-minute overlap on the right.

Munster were favouring the aerial route time and again but O’Gara and Paul Warwick were losing the aerial battle and the visitors’ lineout was unreliable again.

King and replacement scrum half Gavin Cattle injected more energy into the Scarlets’ play. Priestland missed a penalty shot from distance on the hour mark and he had to be nudged into touch, soon after, by Munster replacement Peter Stringer as the Scarlets upped the tempo.

Luck was clearly not on Priestland’s as he watched a 67th-minute drop goal attempt strike the right hand post, but he made amends with a central penalty just a minute later.

Back within a converted score of Munster, the men in red continued to plug away at the breakdown and the Scarlets carved out another kicking chance for their number 10 when Mafi infringed on the deck.

Priestland missed, however, away to the left and Munster breathed a collective sigh of relief as they remained 15-9 ahead.

But their game seemed to be falling apart as a high tackle from O’Driscoll helped the Scarlets set up a lineout in the Munster 22 and then Donncha O’Callaghan saw yellow for preventing a quickly-taken penalty.

With just three minutes of normal time remaining, the Scarlets pounced for a penalty try. Referee Jones signalled for the award after Munster’s replacement hooker Denis Fogarty popped up out of a retreating scrum, just metres from the visitors’ line.

Priestland tagged on the conversion for a sudden 16-15 lead, yet just off the restart, Vernon Cooper was penalised for an off-the-ball challenge and O’Gara brilliantly held his nerve to slam the left-sided penalty through the uprights.

Back in front but still minus O’Callaghan, Munster had to defend feverishly in the closing minutes. They kept their line intact and foiled a last-gasp drop goal attempt from the Scarlets, blocking Ceiron Thomas’ effort, to get back to winning ways in the competition.