The planes took off in bright sunshine from Nato's airbase at Gioia del Colle, in southern Italy, on Tuesday morning.

Daylight missions are known to carry more risk than the night-time raids previously executed by the pilots from the RAF Squadron No 1.

David Shukman: Nato's formidable firepower is constrained by the weather

RAF spokesman Group Captain Ian Travers Smith refused to give any details of the mission.

'All-day operations'

But he said: "It would not take a rocket scientist to realise we have moved into a slightly different phase of operations."

He added that weather conditions were still causing problems to Nato assaults, and said: "We have got aircraft airborne in the daylight at the moment."

Journalists gathered at the base, who were expecting to see the Harriers land, saw one plane taxi away from the runway.

They were then driven back to the press centre at the base. Group Captain Travers Smith said: "I cannot elaborate."

But he said Tornado GR1 planes could also be heading to the base. He addd: "That will give us the capacity to conduct 24-hour operations."

Army targets

As news of the mission was released, the Prince of Wales was visiting the families of the RAF pilots taking part in the Nato bombings.

Prince Charles arrived at RAF Wittering in Cambridgeshire to meet relatives in the officers' mess.

The mission came after poor weather meant overnight strikes by Nato had to be abandoned.

A new phase of intensified 24-hour strikes to force President Milosevic's troops to leave war-torn Kosovo was severely disrupted as Nato forces reportedly targeted army personnel for the first time.

Group Captain Travers Smith said six of the British attack aircraft had been scheduled to carry out bombing raids from the Gioia del Colle base, in southern Italy.

The BBC's Jonathan Charles reports from Italy: Weather was a serious problem

But heavy cloud over the intended target area forced them to turn back within minutes of taking off.

The Harrier pilots also abandoned bombing raids on the first night of the campaign when similar weather conditions affected their laser-guided sights.

Despite the aborted missions Serbian radio reported that Yugoslav forces had shot down what they believed was a Harrier jet over Podgorica, the capital of Montenegro.

"This has been confirmed by locals who have already set out to search for the pilot," it said.

But a Nato spokesman said: "We have heard this report and it is wrong. We have lost no aircraft."

Chief of the Defence Staff Sir Charles Guthrie said that British jets had only managed to strike at their targets on two of the six nights so far.

But he said this refelcted Nato's wish to avoid unnecessary civilian casualties.

'Ethnic cleansing'

The Allied forces have pledged to continue the bombing until Serbia ends its accelerated campaign of "ethnic cleansing", which has resulted in thousands of refugees streaming out of the region.

Nato: Strikes will go on

But Nato has insisted that ground forces will not be required to secure a peace and repel Serb movements in Kosovo.

A poll in the Daily Telegraph newspaper said most people asked (70%) believe Nato will have to consider using ground troops.

But if they are deployed, public support for the allied operation could crumble, said the Gallup survey, conducted last week.

And 52% said they would back the use of ground troops, including UK soldiers, but 40% said they would disapprove.