The overnight strikes came hours before Russia's envoy to the Balkans arrived in the city to try to find a peaceful solution to the conflict.

Nato says it targeted the headquarters of the army and special police and the Ministry of Defence builidng in Belgrade.

Three airfields, a television transmitter south of the capital and three radio relay stations were also attacked by successive waves of Nato bombings.

Nato spokesman Jamie Shea said: "Last night Nato forces hammered the heart of President Slobodan Milosevic's military machine."

Further assaults were carried out against Serb forces in Kosovo and the Novi Sad oil refinery in the north.

Nato also admitted one missile hit a residential area but said they were not aware of the civilian casualties reported by the Yugoslav media.

Bridget Kendall rounds up the diplomatic responses to another night of bombing

The area has also been struck by an earthquake. The tremor shook buildings in the centre of Belgrade, although first reports said there appeared to have been no serious damage.

Earlier, Serbian state television, RTS, went off the air in the middle of its late-night evening news bulletin, following a Nato strike on its main transmitter.

(Click here to see a map of recent Nato strikes)

Russia's special Balkan envoy, Viktor Chernomyrdin, has arrived in Belgrade to discuss his latest peace proposals with President Slobodan Milosevic on Friday.

His visit follows talks on Thursday in Italy and Germany, where all sides reported movement in the search for an agreement.

Mr Chernomyrdin's negotiations with the Yugoslav leader are expected to be dominated by the composition of a possible international peacekeeping force for Kosovo.

Last time, the two sides came away with different views on what had been agreed.

Nato is opposed to Russia's view that air strikes should halt before Yugoslav forces withdraw from Kosovo.

Refugees who recently crossed the Kosovo border into northern Albania are reporting a mass execution in the south-western Kosovo village of Meja.

Eyewitnesses told the BBC that around 300 men were taken from refugee convoys and shot.

The refugees are now being interviewed by aid agencies. War-crimes investigators will also hear their stories.

Oil embargo

There are likely to be further disagreements over Nato's planned oil embargo against Yugoslavia which is due to be put into effect on Friday.

Jon Leyne:"The campaign steadily intensifies"

Speaking at the Pentagon, American Defence Secretary William Cohen said the US was in favour of using force if necessary to stop supplies getting through to Serbia.

However, France says stopping and searching ships would require a United Nations mandate.

Correspondents also point out that Russia has failed to agree to adhere to an embargo.

Bulgarian Ambassador to the UK Valentin Debrov: "Nato needs our support"

Meanwhile the Bulgarian Parliament is beginning a debate on Friday on whether to ratify the government's decision to allow Nato to use some of its airspace for Operation Allied Force.

The discussions follow Nato's admission that one of its missiles had accidentally hit a suburb of the Bulgarian capital, Sofia, on Thursday.

No one was hurt in the incident, but diplomats have described the timing as unfortunate, ahead of the parliamentary debate.

Jackson, Mandela join the talks

The US civil rights campaigner Jesse Jackson is expected to meet Mr Milosevic on Saturday to try to free three captured US soldiers.

Hopeful peace-brokers: President Mandela greets President Yeltsin

Reverend Jackson, who drove to Belgrade despite White House disapproval, said he also hoped to meet the three servicemen.

Meanwhile, Mr Milosevic himself has welcomed an agreement on new peace talks signed by the moderate Kosovo-Albanian leader, Ibrahim Rugova, on Wednesday.

Nato has cast doubt on the deal, saying Mr Rugova is under house arrest and was acting under duress.

In Moscow, United Nations Secretary-General Kofi Annan met President Boris Yeltsin to discuss Russia's role as a peacemaker.

South African President Nelson Mandela, who was also in Moscow, was reported to have agreed to "help mediate in the crisis".

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