Ministry of Defence comments that RAF Harriers GR7s have been able to attack despite thick cloud have led to increased speculation that the Special Air Service is on the ground in Kosovo.

RAF Harrier bombers hit their target

Chief of Defence Staff Sir Charles Guthrie has said improved intelligence on the ground is a factor in the success of raids blocked by heavy cloud.

Nato is in contact with the Kosovo Liberation Army, but Gen Guthrie implied that special forces were active in identifying targets and guiding pilots towards them.

The SAS was widely reported to have worked in the same way during the Bosnian air strikes - although the MoD never confirms or denies SAS operations.

It has also been suggested they will be marking massacre sites, identifying hideouts of death squad leaders and secret weapon arsenals, and rescuing trapped Kosovars.

In Kosovo, the highly-trained soldiers would be split into groups of eight or even smaller cells of four, military strategy expert Nigel Vinson, of the Royal United Services Institute for Defence, told BBC News Online.

They would have been dropped by helicopter behind enemy lines with vital supplies of water and batteries, heavily armed against possible discovery and attack.

"Personal weapons would include hand-held disposable anti-tank rockets, machine guns, rifles and even directional mines on pullcords," said Mr Vinson.

They will be holed up in hillside hideaways carrying out reconnaissance patrols to identify key military transport routes such as crossroads and routes to major town centres.

Laser guidance

"Cells will be there for the duration of the strikes, just sending information once an hour to tell base they are OK," he added.

Colonel Mike Dewar, publisher of Officer magazine and author of some 15 military books, told BBC News Online the special forces would be equipped with laser target markers as a matter of course.

The beam, once picked up by the Harrier, would guide the plane into dropping its bomb into a "basket" without the need to see the target.

But he warned it was dangerous to make much of the likely involvement of the SAS. "These are small patrols of a few people and clearly they are vulnerable.

"They depend on elusiveness and quickwittedness to save their lives.

"If remaining in Kosovo becomes too dangerous they will no doubt withdraw. But they are very capable of looking after themselves.

"In terms of quality of soldiers there is not a single member of the Serb army that comes within 100 miles of their professionalism."