ANCHORAGE, Alaska - An explosion aboard a nuclear-powered Royal Navy submarine under an Arctic ice cap killed two British sailors and injured a crewmember, officials said Wednesday.

In this handout photo provided by the US Navy, Royal Navy submarine HMS Tireless is shown during an exercise in the Arctic Ocean, Saturday, March 17, 2007. [AP]

The forward compartment of the HMS Tireless was damaged in the explosion at 8:20 p.m. local time Tuesday, but the British Ministry of Defense said its nuclear reactor was not affected.

The attack submarine, which does not carry nuclear missiles, was conducting a joint exercise with US forces when its air purification system malfunctioned while the vessel was submerged about 170 miles north of Deadhorse, in northern Alaska's Prudhoe Bay.

According to the US Navy, a self-contained oxygen generation candle exploded.

The submarine surfaced, breaking through the ice, and a private helicopter brought the injured sailor to Deadhorse, where an Alaska Air National Guard aircraft transported him to Kulis Air National Guard Base in Anchorage, 625 miles south.

The sailor's name was not released, but he was reported in stable condition at a civilian hospital.

The Tireless was operating with the USS Alexandria in a joint operation to test submarine operability and tactical development in Arctic waters.

"I am deeply saddened at the loss of the crew members from the Tireless," said US Navy Vice Adm. Jay Donnelly, commander of the Submarine Force. "We stand by to assist in any way we can."

Lt. Col. Andy Price, a Royal Navy spokesman, said the submarine will be evaluated over 12 hours, performing a dive to test its safety systems, before officials decide whether the vessel will continue the joint operation.

It was not immediately clear what went wrong with the air purification system in a forward section of the submarine, a ministry spokesman said while speaking on condition of anonymity in line with government policy.

Since 1986, every Arctic tactical exercise has involved both US Navy and Royal Navy submarines. The current two-week exercise was scheduled to end March 30.