Ireland captain Brian O'Driscoll is facing three to four weeks on the sidelines after fracturing his sinus and suffering a deep laceration under his right eye during a World Cup warm-up match last night.

O'Driscoll was struck by second row Mikaera Tewhata during the second half of Ireland's 42-6 win over Bayonne in France.

Following an x-ray and scan last night, the IRFU confirmed the player had not fractured his cheekbone as first feared.

"This is not as serious as initially feared and the injury will not require any surgery," an IRFU statement released early this morning read.

O'Driscoll will miss the warm-up game against Italy next week and the first World Cup Pool game against Namibia.

But crucially the Ireland captain can train and maintain fitness ahead of the competition, although any work is expected to be non-contact.

The French Rugby Federation are to open an inquiry following the incident.

Eddie O'Sullivan will hope his captain is fit to play the second pool game against Georgia on September 15th.  Last night, however, the Ireland coach was fearing the worst.

"We knew we would get a physical game here, we needed that game. Bar Brian's injury, it was a worthwhile exercise. It'll be overshadowed if Brian got injured (though).

"It was a punch thrown, so you can't legislate for that. Anyone can throw a punch anytime. It could be serious if it is fractured, it would be a pity."

After the incident O'Driscoll was led to an ambulance by his cousin, the team doctor Gary O'Driscoll, to be taken to hospital for a x-rays.

There were further concerns for Ireland with backrow Denis Leamy suffering a shoulder injury but the problem is not considered serious.

Ireland won a physical encounter, which saw five players yellow-carded, thanks largely to a hat-trick of tries from Denis Hickie and two from Paul O'Connell.

Bernard Lapasset, the FFR president,  said he was appalled by the incident and has vowed to open an investigation.

"I haven't the words to describe what I feel," he said.  "This should have been a festival of rugby in a full stadium. Happily we sent an official delegate, a foreign referee.

"I want to know what happened. I will open an inquiry."

Bayonne captain Richard Dourthe felt Ireland were as much to blame for the incidents that took place.

"There was a bit of muscle, but it was muscle on both sides," he said in L'Equipe.  "We responded individually, they did it collectively."