Nato forces stepped up their bombing of Yugoslavia, inflicting a sustained attack on the capital, Belgrade, on Friday night.

Poor weather severely restricted operations of manned aircraft, meaning that the focus of the air campaign was on cruise missiles.

A series of powerful explosions was reported in the city on the third night of consecutive action aimed at persuading Yugoslav President Slobodan Milosevic back down over the Kosovo crisis.

The explosions in Belgrade marked the first attacks on the centre of the city. One of the explosions occured in Kosutnjak, south-west of the city centre, where a military barracks is located.

Several of the capital's suburbs were also reported to have been hit. Belgrade authorities say military targets were hit but also said a pharmaceutical plant was damaged, releasing poisonous fumes.

John Simpson reports from Belgrade: "It is a city with a great deal of anger"

The BBC's World Affairs Editor, John Simpson, one of the few Western journalists to have remained in Belgrade throughout the attacks, reports hearing about 20 explosions overnight.

He said there was no word from the authorities on casualties, which might mean that no people were injured.

At least half-a-dozen explosions were also reported late on Friday in Kosovo's capital Pristina.

Other air raids were said to have targeted the Kosovo towns of Gujilane, south-east of Pristina, Prizren and Djakovica, and the southern fringe of the Montenegrin capital, Podgorica where a military airfield is located.

More strikes on Kosovo

Cruise missiles were launched in the first daylight attack

A Pentagon spokesman in Washington said that around 40% of Nato targets in the latest raids were inside Kosovo - double the percentage in the previous two days' strikes.

"We have been attacking MUP (special police) headquarters and VJ (Serb army) command posts in and around Kosovo," said Ken Bacon.

Friday also saw the first daylight bombing raids and missile attacks on Yugoslavia, with the outskirts of Belgrade being hit during the day.

MiGs 'shot down'

The daylight onslaught on the capital came as Nato reported that it had shot down two Yugoslav fighter planes over Bosnia-Herzegovina.

Andy Tighe reports: "It was the fiercest bombardment yet"

Bosnian Serbs reported that two Nato planes had been shot down, but Nato said there had been no losses so far.

Nato says the pilots of the two MiG-29 interceptors had ejected. Their whereabouts are unknown.

The BBC defence correspondent says the Yugoslav planes appear to have been trying to attack the Nato-led peacekeeping force in Bosnia-Herzegovina.

Bosnia-Herzegovina's ambassador at the United Nations requested an emergency meeting of the Security Council, saying that the Yugoslavia warplanes had crossed into his country "with the intention of committing military strikes against our country".

The Yugoslav Foreign Minister, Zivadin Jovanovic, denied that the fighters were shot down.

He also accused Nato of killing dozens of civilians.

Reprisals

As reports surfaced that Serb forces were retaliating against Kosovo Albanians for the Nato attacks, Washington officials said there would be a price to pay for any reprisals.

Alan Little on the build-up to the current crisis

State Department spokesman James Rubin said: "The United States is extremely alarmed by reports of an escalating pattern of Serbian attacks on Kosovar Albanian civilians."

There have been reports of atrocities by the Serb forces with residents and aid workers speaking of people being rounded up and shot, and of widespread looting and burning of buildings.

However Serbian reports have maintained that the separatist Kosovo Liberation Army (KLA) has been using the cover of Nato strikes to launch attacks on Serbian positions

Massacre reports

Nato Supreme Commander General Wesley Clark said the air campaign would now quickly shift to attacking formations in the field.

So far, Nato's military action shows no signs of halting attacks by Serbian forces in Kosovo. The UN refugee agency has expressed grave concern at reports of massacres of Kosovo Albanian civilians.