Three casualties from a stricken Canadian submarine off the northwest coast have been airlifted to Sligo General Hospital.

The three are believed to be suffering the effects of smoke inhalation. One man's condition has been described as critical.

There is speculation that a request may be made to bring the submarine into Blacksod Bay in Co Mayo for shelter.

The HMCS Chicoutimi, with 57 crew on board, had been drifting without power off the northwest coast of Ireland.

The British naval frigate reached the submarine this afternoon, and several other Irish and British naval vessels also converged on the scene.

High winds and heavy seas had hampered efforts to reach the submarine, which issued a mayday call yesterday afternoon.

A fire had knocked out its engines and nine crewmembers suffered from the effects of smoke inhalation.

The vessel is a refitted British submarine, formerly HMS Upholder, which only officially joined the Canadian Navy five days ago under a deal agreed in 1998.