Wales defeated Ireland 23-16 to maintain their hopes of becoming Six Nations champions, while the holders saw their hopes of a Grand Slam ended in Cardiff.

The home side's victory - earned thanks largely to replacement Scott Williams' try and five penalties from Leigh Halfpenny - moved them level with Ireland on three wins from four matches.

Ireland are 21 better off in terms of points difference, while this result also opens the door for England to enter the equation and potentially set up a three-way race for the title in the final weekend of action.

The visitors were left to rue a nightmare start, as four Halfpenny kicks earned Wales a 12-0 advantage inside the opening 15 minutes.

Williams' score midway through the second period saw Wales move 20-9 in front and although a penalty try six minutes later brought Ireland within four, another Halfpenny kick sealed victory for Warren Gatland's side.

The only early blow for Wales was losing prop Samson Lee, who had to be carried from the field on a stretcher and later emerged on crutches with a protective boot on his left leg.

Ireland had got on the board by that point through a Jonathan Sexton penalty.

Wales captain Sam Warburton was sin-binned for going off his feet 12 minutes before the break, and Sexton knocked over the resulting kick to bring Ireland within six.

Dan Biggar's drop-goal and another kick from Sexton made it 15-9 at the break.

At the start of the second half, Ireland put Wales under intense pressure inside their own 22 but they could not secure the try as an infringement gave Wales the chance to clear their lines, which was met by a roar of approval from the partisan crowd.

Wales responded strongly, Jonathan Davies' break getting them deep inside Ireland territory, but Biggar's long pass out to Halfpenny was too long and the chance went begging.

However, Wales stole the resulting line-out and Williams took a pass from Biggar and darted between Jamie Heaslip and Tommy Bowe to touch down in the 63rd minute.

Halfpenny missed the extras and, with 11 minutes to go, Ireland's driving maul forced a penalty try which was converted by Sexton, and the visitors were back within four points.

Just as it seemed Ireland would mount a stirring fightback, they were penalised for not releasing and Halfpenny slotted the kick to give Wales some breathing space.

Two minutes from time, Davies was sin-binned for a deliberate knock-on but the 14 men withstood fierce pressure to hold out and blow the title race wide open.