At the Berlin summit of EU heads of state, the Prime Minister said the Western alliance was taking action "for one very simple reason - to damage Serb forces sufficiently to prevent Milosevic from continuing to perpetuate his vile oppression against innocent Albanian civilians". He added: "Nobody can say either that we have not tried to find a peaceful settlement or that Milosevic has not been warned of the consequences of continuing his suppression of the people of Kosovo."
The Deputy Prime Minister, John Prescott, confirmed in an emergency statement to the Commons that six RAF ground attack Harrier GR7 aircraft, with cruise missiles from the submarine HMS Splendid, had taken part in the bombing campaign.
Although the British people "take no joy in war", Mr Blair added, "we know from our own history, and from our own character, that there are times when we have to stand up and fight for peace".
Gerhard Schroder, the German Chancellor and first German leader to authorise military action since 1945, went on national television saying Nato stood ready "to defend the common, basic values of freedom, democracy and human rights. We cannot allow these values to be trampled under foot less than an hour's flight from us... Our determination to end the killing in Kosovo is beyond doubt". The French President, Jacques Chirac, said the air attacks were launched to defend "peace on our soil, peace in Europe".
Mr Blair stressed that of the 13 nations that have made aircraft available, eight were in action, but he made no mention of the reservations of the neutral European nations. They are concerned that the action was not covered by a specific UN resolution. Austria, which closed its airspace to the military operation, said the action had no mandate under international law.
Ireland's Foreign Minister, David Andrews, described the attacks as "tragic" and "regrettable", but declined to comment on their legality. His Swedish counterpart, Anna Lindh, argued that the raids "would not be entirely covered by international law" but added: "I can understand the political situation."
Earlier, Europe's leaders managed to unite with a condemnation of Mr Milosevic in a statement that failed to issue a collective endorsement of air strikes. Issued just hours before the bombing of Serb targets in Kosovo, the statement from Europe's foreign ministers said it was "not too late to stop the internal repression and to accept the international community's mediation efforts". But it also insisted that the international community would not tolerate "crimes against humanity". "On the threshold of the 21st century, Europe cannot tolerate a humanitarian catastrophe in its midst," the statement said. "It cannot be permitted that, in the middle of Europe, the predominant population of Kosovo is collectively deprived of its rights and subjected to grave human rights abuses. We, the countries of the European Union, are under a moral obligation to ensure that indiscriminate behaviour and violence, which became tangible in the massacre at Racak in January 1999, are not repeated... An aggressor must know that he will have to pay a high price. That is the lesson to be learnt from the 20th century."
References to Western military action were removed at the request of Austria, Sweden, Finland and Ireland.
Joschka Fischer, Germany's Foreign Minister, rejected the idea that the failure to mention the military option weakened the credibility of the EU's position. Mr Fischer said: "Air strikes are demanded by Nato, not the EU. This is a strong statement of solidarity. It is not at all weak. Many, but not all, members of the EU are members of Nato."
The Greek Prime Minister, Costas Simitis, dismissed statements by the United States and Britain that violence in Kosovo could eventually drag his nation into conflict with its Nato ally, Turkey. Mr Simitis said he had told the summit that he disagreed with the view advanced by Bill Clinton and Mr Blair.
"Mr Clinton's view is not justified by any means." He added: "Greece is a peacemaking, stabilising force in the area. There is no reason for anyone to fear that there will be implications with Turkey."
John Prescott, the Deputy Prime Minister, last night compared recent Serb aggression in Kosovo to the build-up to the Second World War. He said recent harrowing images from newspapers, with "scenes more reminiscent of the Middle Ages than of Europe on the eve of the 21st century", had proven the need to act urgently. He told a packed and sombre House of Commons that the West was not waging a war against the Yugoslav people.
The Prime Minister, on his return from Berlin today, will face renewed questions about what will be done if the air strikes fail. On Tuesday, Mr Blair told the Commons that it would take more than 100,000 troops to wage a land war against the Serbian army.
and Colin Brown