DUBLIN Feb 5 (Reuters) - Leigh Halfpenny's last-minute penalty gave Wales a 23-21 win over Ireland in an enthralling Six Nations see-saw battle on Sunday as the hosts failed to avenge last year's World Cup quarter-final defeat.
Wales, missing several first-team players, were well on top in the early exchanges of their championship opener.
Ryan Jones was denied a try by the video referee before Jonathan Davies was adjudged to have got the ball down after a superb offload by Rhys Priestland, who struck the post with the conversion and a penalty.
Ireland, without the injured Brian O'Driscoll, hit back with a Rory Best try after a great Tommy Bowe dummy just before halftime only for Davies to grab his second touchdown after the break as Wales led.
Bowe put the Irish clear with his own try on 68 minutes but George North went over for Wales late on to move within a point.
Stephen Ferris then joined Bradley Davies in the sin bin as both were punished for dangerous tackles and Halfpenny slotted the penalty through the posts for a dramatic victory.
"That was the hardest kick I've had to kick in my life," Halfpenny told the BBC.
Ferris's offence was an arguable yellow card while Wales' Davies could easily have seen red for his spear tackle.
"We obviously put ourselves in a great position to win it," Ireland captain Paul O'Connell said.
"There was a bit of work left to be done and we didn't do it."
Irish flyhalf Jonathan Sexton, playing instead of Ronan O'Gara, opened the scoring with a penalty after three minutes and Ireland were lucky to maintain their lead when Welsh flanker Jones crossed the line minutes later.
The video referee ruled it was unclear if he had touched down.
Wales though forced their way onto the scoreboard after 13 minutes when Priestland dashed past two players before offloading to Jonathan Davies, who put down in the corner.
Despite dominating most of the first half, Wales failed to capitalise with Priestland hitting the posts on the conversion and with a penalty right in front.
Ireland stirred in the minutes before halftime and landed a sucker punch when a string of passes allowed Bowe to step inside his man to set up Best for a try.
Sexton converted to leave Ireland leading 10-5 at the break and then extended the advantage with a penalty three minutes into the second half as Wales came out without injured captain Sam Warburton.
Wales fullback Halfpenny took over kicking duties given Priestland's problems and scored his first penalty in the 53rd minute.
The visitors roared further back into gear just before the hour when a backhanded offload by North set up Jonathan Davis for a 30-metre run to touch down behind the posts. An easy Halfpenny conversion put Wales back into the lead.
Ireland clawed back three points after a blistering attack set up Sexton for a penalty to leave a point in it before Welsh lock Bradley Davies was sent to the sin bin in the 65th minute for a spear tackle.
Ireland capitalised on the extra man, Donnacha Ryan stealing a Welsh line out in their 22. After the forwards failed to cross the line, the Irish back line passed across the field for Bowe to score the try, which Sexton failed to convert.
North then powered his way over the line in the 75th minute but Halfpenny missed the conversion to leave Ireland one point ahead in a cliffhanger finish.
In the dying minutes, Ferris was yellow carded for a dangerous tackle and Halfpenny put the penalty between the posts amid jeers from the Dublin crowd.
England beat Scotland and France overcame Italy on Saturday's opening day of matches.
Ireland travel to France next Saturday while Wales host Scotland on Sunday. (Editing by Mark Meadows; To query or comment on this story email email@example.com)