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As Serbia woke up after the biggest aerial bombardment in Europe since World War II, Nato's Secretary-General Javier Solana has warned that strikes will probably continue for "a few more days".

Nato strategists are assessing the aftermath of the first wave of attacks amid strong criticism at the UN Security Council and a declaration of war by the Yugoslav army.

Mr Solana, speaking on French radio, said Nato would give a briefing at around 1100 GMT. Asked about how long the strikes would continue, he said: "It is very difficult to give a precise duration. I hope it will be very soon. We are talking about days, not months."

The western military alliance delivered its answer to President Slobodan Milosevic's continued refusal to sign a peace deal by launching Operation Allied Force - firing Cruise missiles in the first wave of a major offensive.

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During the night, the Belgrade sky was lit up with tracer fire from anti-aircraft batteries in what was the first attack on a European capital since 1945.

All-clear sirens sounded as dawn broke in the Yugoslav capital, Belgrade and a semblance of normal life began to return.

During the night Nato forces pounded military positions. One local radio station had reported intense activity by Nato aircraft in the Belgrade region

Jacky Rowland describes a surprisingly normal scene today after bombardments from the night before

Other targets of Nato's first attack on a sovereign European country included sites in Kosovo itself and Montenegro, Serbia's smaller partner in the Yugoslav Federation.

In Kosovo's regional capital, Pristina, air raid warning sirens are reported to have again gone off this morning.

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Residents endured a complete loss of power after air strikes and air raid sirens were reported through the night.

This morning, power was restored and life was reported to be returning to normal with buses operating and people heading to work.

State of war

The Yugoslav army said 40 targets were hit in three hours including five airports, five barracks, communications and command positions.

The BBC's Kate Adie reports on witnessing the attacks start

Families of military personnel had died in the attacks and Serbia had declared a "state of war" against Nato, the army said. National television broadcast pictures of burning buildings throughout the country and what were reported to be victims in hospital.

The Yugoslav army also said that the Kosovo Liberation Army, fighting the Serbs for an independent Kosovo, was amassing a large force to take advantage of the strikes.

The BBC's Jon Devitt reports on the first wave of the air strikes

The Pentagon said allies had downed at least one Yugoslav MiG fighter.

But it denied reports that up to two Nato aircraft were lost.

Chairman of Nato's military committee, General Klaus Naumann,said all Nato aircraft which took part in strikes on Yugoslavia returned safely to their bases.

Damage reports

Attacks were led by US and UK war ships in the Adriatic Sea working with B-52 bombers launching Cruise missiles.

They were joined by new B-2 stealth bombers from Missouri, USA.

Germany provided four aircraft - the first time that it has entered combat over foreign territory since WWII.

In total, eight Nato countries provided firepower for the attacks.

Among the known targets were:

• The large Batajnica military air base near Belgrade.
• A suspected military aircraft factory near the capital.
• Targets in Novi Sad, north of Belgrade
• The Zastava weapons plant, Kragujevac.

Casualties: Those said to be injured shown on Serb TV

BBC reports from Kosovo indicate that Nato targeted Serb units in two towns which have been involved in ground attacks on ethnic Albanian villages.

Communications with the outside world have been severely hit with journalists at times unable to report the latest situation.

During the evening, Serb police arrested up to 20 journalists as they filmed attacks from the roof of a Belgrade hotel. They were later released.

'Moral imperative'

Addressing the American people, President Bill Clinton said that western allies had to fulfil a moral imperative over Kosovo.

Mark Devenport reports from Washington on the media blitz to win round the US public

"If President Slobodan Milosevic will not make peace, we will limit his ability to make war," he said.

"We act to prevent a wider war, to defuse a powder keg at the heart of Europe."

Defiance

However, in an emergency meeting of the United Nations' Security Council, Russia and China led condemnations of Nato's action, describing it as a violation of international law.

President Boris Yeltsin recalled Russia's representative at Nato's Brussels headquarters and ordered a halt to all co-operation with the alliance.

Speaking hours before the attacks, President Milosevic called on his people to be prepared to defend their country "by all means".

In a nationally televised address he warned them that "at stake is the freedom of the entire country".