Ireland were outscored on the try count by three to two, but battled their way into a 21-15 lead thanks to touchdowns from Rory Best and Tommy Bowe and 11 points from the boot of Jonathan Sexton.

However, Wales' dominance of possession and dangerous backs kept them in the hunt and an unconverted try from George North (76 minutes) and Halfpenny's late heroics saw them take the spoils.

Both teams suffered yellow cards with Bowe crossing for his try while Welsh lock Bradley Davies was in the sin-bin for a spear tackle on Donnacha Ryan.

Referee Wayne Barnes might have produced a red card such was the dangerous nature of Davies' challenge, which saw Ryan land on his neck/shoulder area.

It was a moment of controversy in an otherwise cleanly-fought game that brought together the vast majority of the players who contested the Rugby World Cup quarter-final in Wellington last October.

There were a few notable absentees with captain Brian O'Driscoll heading the Irish injury list and the Welsh engine room missing crocked locks Alun-Wyn Jones and Luke Charteris.

Paul O'Connell took on the captaincy role for Ireland, and also set a new RBS 6 Nations record for a second row combination with his 21st start together with Donncha O'Callaghan.

Fergus McFadden slotted in for O'Driscoll at outside centre, making his third Championship appearance, and Ireland made the early headway with Bowe clattering into Mike Phillips as his former club-mate collected a high ball.

A ruck infringement by Ryan Jones allowed Sexton his first shot at the posts and he duly delivered the first points of the match, handing Ireland a fourth minute lead.

But Wales wasted little time in mounting a response. Bradley Davies had to be hauled down in the Irish 22 after a well-worked lineout and North and Phillips both went close before Ryan Jones was held up over the try-line.

Gatland's side continued to put pressure on Ireland and they worked bustling centre Jonathan Davies over for his first try in the 14th minute. He crossed in the left corner after taking Priestland's well-timed offload out of a tackle.

Television match official Geoff Warren confirmed the score and Priestland was unfortunate to see his conversion attempt bounce back off the right hand post.

Wales had begun to build a solid platform with their forwards clearing out well, Phillips providing a series of snappy passes and their backs beginning to stretch the Irish defence.

Sean O'Brien was pinged for playing the ball off his feet at a ruck, offering Priestland a penalty shot from straight in front of the posts but the out-half blundered when cannoning his kick off the left upright.

It was a let-off for Ireland and there some encouraging signs for Declan Kidney's men with Rob Kearney rising high to gather a garryowen and O'Connell and Jamie Heaslip gragging a couple of lineout steals.

Sexton failed to punish Alex Cuthbert for holding onto possession on the deck, missing a right-sided penalty on the half hour mark.

Andrew Trimble came more into the game with some good covering on his wing and as Ireland clawed back territory, the Ulsterman showed his potential with ball in hand.

The home crowd could sense an improvement in Ireland's play when Ryan Jones was held up in contact by a combination of Ferris, O'Callaghan and Sexton. The next phase saw the men in green charge into the visitors' 22, but Cian Healy lost the ball forward.

Nevertheless, the momentum was still with Ireland and after Trimble initiated a counter attack from deep, Kidney's charges put together their best attacking phase.

Slick hands from Gordon D'Arcy and neat footwork from Bowe, on the end of a free-flowing move, sent hooker Best cantering over to the left of the posts. Sexton added the conversion to make it 10-5 at the interval.

A leg injury forced Welsh skipper Sam Warburton off at half-time, bringing Justin Tipuric into the fray and James Hook was also sent on at full-back with Halfpenny moving to the right wing.

Ireland started the second period at a high intensity and a good hit from the scrum forced Rhys Gill to drop his bind, with Sexton landing the resulting penalty for a 13-5 advantage.

Despite a lengthening injury list, Wales were up for the fight and Priestland should have done better with a long range penalty attempt that he spiralled away to the right.

Four minutes later, Halfpenny was called upon to try his luck from distance. The possessor of a fine right boot, the Cardiff Blues star thumped over a well-judged kick to close the gap back to five points.

It got even better for Wales as they used first phase ball from a lineout to smash their way through for a second try. North was unleashed and he fended off McFadden's challenge before popping an inviting offload to Davies who had a pace to finish off a superb attack.

Halfpenny's conversion nudged Wales into a 15-13 lead. Yet Ireland were swiftly back on the front foot, Kearney's impressive catch and offload helping Conor Murray to set up a left wing raid which saw Heaslip involved twice.

The rewarded for a concerted spell of possession and territory was another penalty from Sexton which he squeezed inside the right hand post.

Five minutes later, Bradley Davies received his marching orders from Barnes following his part in an off-the-ball incident. With O'Connell, Ferris and Heaslip all carrying well, Ireland were poised to take full advantage of the indiscretion.

Replacement Ryan picked off a Welsh lineout in the 22, sending O'Connell peeling away and Best was a metre away from scoring his second. Ireland kept their composure and Sexton's switch of direction out to the right led to Kearney passing for Bowe to dive over in the corner.

Sexton drew his conversion attempt away to the left but with less than ten minutes remaining, Ireland had a six-point lead and a one-man advantage.

Heaslip then forced Gill to concede a penalty at a ruck a couple of metres inside the Irish half. A further three points would have given Ireland a bit more comfort in the closing stages. However, in going for additional power, Sexton sent his kick to the right and wide.

In response, Priestland found an excellent touch from a penalty. Lock Ian Evans managed to find a gap and bring Wales into the hosts' 22, and Ireland's defence was breached again as a string of passes out to the left ended with North muscling over past D'Arcy and Bowe.

Halfpenny failed to add the conversion from a difficult conversion, leaving Ireland to defend a one-point margin in the dying minutes.

The home victory was agonisingly close when Barnes penalised Ferris for his tackle on Evans, handing Halfpenny a last-minute opportunity which he coolly took.

His successful kick from in front of the posts condemned Ireland to their first loss in an opening round Six Nations match since 2004, and ended their hopes of winning a Grand Slam or Triple Crown this season.

The result also marked the first time Wales have beaten Ireland in three successive Tests since 1979, with Kidney's side now needing to recover quickly for next Saturday's showdown with France in Paris.