The ruling immediately brought a chorus of international condemnation and could prove to be a setback for Libya's efforts to improve ties with the West.

Bulgaria's foreign ministry called the decision "deeply disappointing" and urged Libya's leadership to intervene in the case and free the nurses.

Bulgaria has maintained that the children were infected by unhygienic conditions at the Benghazi hospital, in the north of Libya, where they were being treated.

"Sentencing innocent people to death is an attempt to cover up the real culprits and the real reasons for the AIDS outbreak in Benghazi," said Georgi Pirinski, a Bulgarian parliamentary speaker.

However, shouts of joy met the decision in the Tripoli courtroom.

"God is great!" yelled Ibrahim Mohammed al-Aurabi, the father of an infected child, as soon as the verdict was announced. "Long live the Libyan judiciary!"

The five Bulgarians and Palestinian were accused of infecting 426 Libyan children with HIV at a hospital in Benghazi in the late 1990s.

The medics, who denied the charge, have all been detained for nearly seven years. The five Bulgarian nurses are Snezhana Dimitrova, 54, Alia Cherveniashka, 51, Nasya Nenova, 40, Christiana Valcheva, 47, and Valentina Siropoulo, 47. The Palestinian doctor is Ashraf Alhajouj, who is in his late 30s.

They were previously sentenced to death by firing squad in 2003, but that conviction was overturned last year following international protests over the fairness of the proceedings.

It is likely that they will appeal against today's verdict to the Libyan Supreme Court.

Judge Mahmoud Haouissa did not say how they would be executed.

International legal observer, Francois Cantier of Lawyers Without Borders, criticised the retrial for failing to admit enough scientific evidence. He said samples from the infected children showed that their viruses were contracted before the six defendants started working at the hospital in question.

"We need scientific evidence. It is a medical issue, not only a judicial one," Mr Cantier said after the verdict.

Dr Luc Montagnier, who is credited with discovering HIV, had testified in the first trial that the deadly virus was active in the hospital before the Bulgarian nurses and Palestinian doctor began their contracts there in 1998.

Nature magazine also published an analysis of HIV and hepatitis virus samples from the children earlier this month, which concluded that the virus was contracted up to three years before the six defendants arrived at the hospital. But it was too late to be submitted as evidence in the trial.

The long trial has hampered oil producer Libya's rapprochement with the West, which moved up a gear when it abandoned its pursuit of nuclear, chemical and biological weapons in 2003.

The United States and the European Union, which Bulgaria is due to join on January 1, have both called for the defendants to be released citing evidence that they were tortured to confess and that evidence points to the virus being present at the hospital before their employment.

Franco Frattini, the European Union Justice and Security Commissioner, said he was shocked and disappointed by the ruling and Amnesty International has also condemned the decision.

Relatives of the infected children - about 50 of whom have already died of Aids - waited outside the court early this morning, holding poster-sized pictures of their children and bearing placards that read "Death for the children killers; and "HIV made in Bulgaria."

After the verdict, relatives at the court gates chanted "Execution! Execution!"

Many parents have demanded compensation or "blood money" of up to $13.10 million for each infected child to quash the verdicts. Bulgaria has refused to pay, saying that doing so would be an admission of guilt.

In Bulgaria, hundreds of people staged peaceful protests in support of the five nurses yesterday.

Their families were distraught on hearing the verdict. "This is such a disgrace. I simply cannot believe that such injustice can be done," said Polina Dimitrova, daughter of Mrs Dimitrova. "I can only imagine how they feel - this must have crushed them."

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