The Duke of York has led tributes to the six British servicemen killed when two Royal Navy helicopters collided over the Persian Gulf on Saturday.

The former Royal Navy Flight Commander, who flew Sea Kings in the Falklands conflict, said he was "shocked and deeply saddened" by the accident and sent his prayers to the families of those who died.

A US officer also perished in the collision when two Sea King helicopters crashed shortly after taking off from the Ark Royal carrier.

The Ark Royal's Captain Alan Masey said the deaths were caused by a "tragic accident" and said the loss on board the Royal Navy's flagship "is being felt very intensely."

The cause of the crash was under investigation but they were not hit by enemy fire a spokesman for the British forces in the Gulf said.

Group Captain Al Lockwood said: "All those on the helicopters have perished. It is a great tragedy.

"We do have very careful plans and procedures to ensure we have separation of all the aircraft being used.

"Sadly, last night something was not quite right and we are looking to find out what that was as quickly as possible."

Pentagon spokesman Major Ben Owens said a US Navy officer was among the victims.

A statement from Downing Street expressed "deep sadness" at the loss of more military personnel.

Eight Royal Marines and four American Marines became the first casulaties of the invasion of Iraq when their CH-46 Sea Knight helicopter crashed before dawn in Kuwait on Friday.

Lieutenant Colonel Ben Curry, a Royal Marines spokesman, said that crash occurred as troops were being deployed to seize the al-Faw peninsula in southern Iraq.

Three members of an ITV News crew were missing in Iraq on Saturday after their car came under heavy fire near Basra.

Efforts were being made to find British TV reporter Terry Lloyd, a camerman and translator who were covering the Allied advance on Iraq's second city.

Iraq in depth: iraq.usatoday.com