The USS Hartford, seen in this file photo, collided with an amphibious ship in the Strait of Hormuz between Iran and the Arabian peninsula early Friday. (Don S. Montgomery/U.S. Navy/Associated Press)

Two U.S. navy vessels — a nuclear-powered submarine and an amphibious ship — collided early Friday in the Strait of Hormuz between Iran and the Arabian peninsula, the U.S. navy's 5th Fleet reported.

There was no damage to the sub's nuclear propulsion system, said Lt. Nate Christensen, a 5th Fleet spokesman.

The military said in a statement that the incident occurred around 1 a.m. local time on Friday (5 p.m. ET Thursday), when the USS Hartford, a submarine, and the USS New Orleans, an amphibious ship, collided.

The amphibious transport dock ship USS New Orleans was heading to port when the collision occurred. (Lt. j.g. Jared Apollo Burgamy/U.S. Navy/Associated Press)

According to the Bahrain-based 5th Fleet, 15 sailors aboard the Hartford were slightly injured but able to return to duty. No injuries were reported aboard the New Orleans.

Both ships were heading to port and were going in the same direction when the incident occurred in the narrow strait, said Christensen. He said the incident occurred at night and the submarine was submerged at the time but that he could give no further details as the collision is still under investigation.

Both vessels are now heading to port for repairs and evaluation, but Christensen said that following standard security procedures he could not say where the vessels were headed.

95,000 litres of fuel spilled

The New Orleans suffered a ruptured fuel tank, resulting in an oil spill of approximately 95,000 litres of diesel fuel. There was no damage to the nuclear reactor powering the Hartford, Christensen said.

Both ships are currently operating under their own power.

The navy said both ships were on regularly scheduled deployments to the region and conducting security operations.

Oil prices rose after news of the collision, which happened in a busy shipping route.

As much as 17 million barrels of oil a day went through the narrow strait in the first half of 2008, or about 40 per cent of all seaborne traded oil or 20 per cent of all oil traded globally.

The Hartford is based in Groton, Conn., and the New Orleans is based in San Diego, Calif., the navy said. The Hartford is nuclear-powered, as are all active U.S. submarines. The New Orleans is an amphibious transport dock ship.