The attack on the building in the centre of Belgrade - which contradicted an apparent assurance by Nato this month that only transmitters would be hit - was condemned by international journalists' organisations, representing both employers and unions.

Reporters at the scene said they saw the almost decapitated body of one man dangling from the rubble, and the body of a make-up artist. Another man was trapped between two concrete blocks. Doctors amputated his legs at the site but he later died.

The state-run news agency Tanjug said about 150 people were inside the building at the time of the attack. The minister without portfolio, Goran Matic, said that in addition to 10 dead and 18 wounded, at least 20 people were feared buried in the rubble.

Officials said the missile also destroyed a satellite link with Eurovision used by foreign television crews to transmit material abroad, though the station was back on the air in Serbia within six hours.

The attack was the latest in a series of controversial targets, and followed the bombing of President Slobodan Milosevic's house on Thursday and an attack the previous day on the Serbian Socialist party's headquarters building, which also contained the offices of television stations run by members of his family or people close to his regime.

Tony Blair, in Washington for Nato's 50th anniversary summit, insisted that bombing television stations was 'entirely justified' since they were part of the 'apparatus of dictatorship and power of Milosevic'. He added: 'The responsibility for every single part of this action lies with the man who has engaged in this policy of ethnic cleansing and must be stopped.'

At a heated press briefing at the Ministry of Defence, Clare Short, the international development secretary, said: 'This is a war, this is a serious conflict, untold horrors are being done. The propaganda machine is prolonging the war and it's a legitimate target.'

Admiral Sir Ian Garnett, chief of joint operations at the ministry of defence, said Mr Milosevic's 'propaganda machine consists of transmitters but also the studios from which the information is transmitted. That makes it part of the overall military structure. Both elements have to be attacked.'

Nato's military spokesman, Air Commodore David Wilby, two weeks ago described RTS, the Serbian state broadcasting station, as a 'legitimate target which filled the airways with hate and with lies over the years'. However, Jamie Shea, the Nato council spokesman, denied that RTS was a target, distinguishing between transmitters 'integrated into [military] command and control commmunications' and normal broadcasting facilities.

On April 12, Mr Shea told Aidan White, the general secretary of the International Federation of Journalists, that Nato would 'target military targets only. Television and radio towers are only struck if they are integrated into military facilities, as they often are in Yugoslavia,' he said, but added: 'There is no policy to strike television and radio transmitters as such.'

In a statement yesterday, the IFJ condemned the attack, warning that it could lead to reprisals against independent journalists who have been campaigning against controls imposed by the Milosevic regime. 'We have been trying to trace journalists who have gone missing or been detained by the Serb authorities. Their plight is made ever more perilous by this latest strike,' it said.

John Foster, general secretary of the National Union of Journalists described the attack as 'barbarity'. He added: 'Killing journalists does not stop censorship, it only brings more repression.' Peter Almond, chairman of the Defence Correspondents' Association, expressed 'considerable disquiet', particularly in the light of Mr Shea's assurance to the IFJ.

In Geneva, the European Broadcasting Union, which groups the main stations in and around Europe, said the Belgrade television centre had been used to transmit news reports by international as well as local media. 'We do not see how the suppression of news sources can serve any useful purpose,' the EBU's president, Albert Scharf, said.

'Over and beyond the deaths involved, the EBU is concerned about any attempts to limit the rights of audiences to full news services.'

Bulgaria said yesterday that a Nato air-to-ground missile fell almost halfway between the border with Yugoslavia and the capital Sofia on Thursday.