Already the nation's all-time record goalscorer, Keane claimed his 47th and 48th goals in his 106th appearance for the national team.

At the other end of the scale, Wolves utility man Stephen Ward and West Brom striker Simon Cox marked their debuts with their first international goals, while Craig Cathcart netted an own goal and Adam Thompson saw red.

It proved to be a disappointing night overall for Northern Ireland, who were cheered on by a sparse band of supporters after fans staged a boycott in protest at travelling restrictions placed upon them.

Ward was not in the team that manager Giovanni Trapattoni named to the media yesterday, meaning he was a surprise inclusion in the starting XI at the Aviva Stadium.

As Ward and Cox both made their maiden bows for the Republic, teenager Josh Carson was handed his first cap for Northern Ireland and Gareth McAuley was named as captain.

The visitors had the first real chance on goal but Jonny Gorman was well off-target with a shot that he sliced past the post.

At the other end, Seamus Coleman's cross picked out Paul McShane in front of goal but he sent his header flashing past the upright.

The Republic were threatening again when Keith Treacy unleashed an effort from distance but the shot lacked power and it was comfortably smothered by Alan Blayney.

The hosts continued to press and were only denied the opener by the woodwork when Cox cut the ball back for Keith Andrews and his swerving effort smacked off the post.

The home side's hard work paid off when they took the lead with 24 minutes gone. Treacy played a one-two with Cox from a short corner before whipping into the goal-mouth. Goalkeeper Blayney threw himself at the ball but spilled in front of Ward who rifled home the opener from close range.

The Republic doubled their lead after 37 minutes when Keane pounced on a dreadful pass-back by Lee Hodson before lofting over the goalkeeper and seeing the shot nestle in the bottom corner.

There was further misery for Northern Ireland when Coleman's ball across the face of goal was forced into the back of his own net by Cathcart a minute before the interval.

The Republic were always favourites to come out on top and added to their tally nine minutes after the restart.

Thompson was deemed to have fouled Keane in the box and was given a straight red card by Scottish referee Craig Thomson, before the Tottenham striker dusted himself off and slotted low past Blayney from the penalty spot.

Keane could have claimed a hat-trick with a ferocious volley but, this time, the goalkeeper was up to the task and produced a decent save. Keane was then replaced by Andy Keogh to rapturous applause from the crowd.

A commotion then followed in the section housing the Northern Ireland fans, however order was quickly restored by the stewards.

It had been an uneventful night for Shay Given in the Republic goal and he was replaced by David Forde for the final 20 minutes.

But Blayney was left picking the ball out of the back of the net again when Cox raced into the box and sent an angled drive past the goalkeeper to complete the rout, before Stephen Hunt's free-kick crashed off the post late on.

The victory put the Republic at the top of the Nations Cup table ahead of Scotland's game against Wales tomorrow night.