Ireland and Munster second row Paul O'Connell has been ruled out of action for six months.

O'Connell who shot to prominence last season as a rookie during Munster's run to the Heineken Cup final, underwent back surgery in Cork on Monday.

He will miss the entire Celtic League campaign, the pre-Christmas Heineken Cup matches, Ireland's World Cup qualifiers and the autumn internationals against Australia, Fiji and Argentina.

It is a further blow for the new Munster coach Alan Gaffney who had already lost Lions back row David Wallace for a similar period.

Munster have so far made two pre-season signings.

Backroom role

Australian prop Simon Kerr has moved to the Irish province following the retirement of veteran front row star Peter Clohessy.

And scrum-half Dom Malone joined from Northampton as back-up to Peter Stringer.

With Mick Galwey in semi-retirement and looking to develop a backroom role, it leaves only Donncha O'Callaghan and Mick O'Driscoll as recognised second row forwards.

Munster manager Jerry Holland conceded that a new lock forward was now an urgent priority.