The presiding judge, Mahmoud Hawissa, read out the verdict in a seven-minute hearing at a Tripoli court, which came at the end of the defendants' second trial.

The six - who had detained for nearly seven years - had previously been convicted and sentenced to death, but Libyan judges granted them a retrial after international protests over the fairness of the proceedings.

Bulgaria says the children were infected by unhygienic practices at their Libyan hospital.

The accused now have the right to appeal to the Libyan supreme court. If it upholds the sentence, the only hope the medics have left is of a pardon.

The long trial has become a bone of contention in the efforts of the Libyan leader, Muammar Gadafy, to rebuild ties with the west. The EU and US have called for the six to be released, indicating that future relations with Triploi would be affected by the verdict.

However, the case is emotive in Libya, where it is seen less as an indication of how far Colonel Gadafy will go to boost his standing with the west than as the trial of people accused of infecting children with HIV.

Relatives of the infected children - around 50 of whom have already died of Aids - waited outside the court early today. They held poster-sized pictures of their children and placards that read "Death for the children killers" and "HIV made in Bulgaria".

When the supreme court ordered a retrial in December 2005, friends and relatives rioted in Benghazi, the Libyan city in which the children were infected at a state hospital.

Hundreds of people in Bulgaria staged peaceful protests in support of the five nurses yesterday. The EU, the US and international rights groups have accused Libya of prosecuting the six foreign staff - who were first sentenced to death by firing squad by a Libyan court in May 2004 - as scapegoats.

Amnesty International today urged the Libyan authorities to declare that the death sentences would not be carried out.

"In this trial, as in their earlier one, confessions which they have repeatedly alleged were extracted from them under torture were used as evidence against them," Malcolm Smart, the Middle East and North Africa programme director, said.

"Defence lawyers were not allowed to bring in international expertise, and the evidence produced by Libyan medical experts was questioned by international medical experts.

"Only a fair trial can bring out the truth and do justice to the children who have been infected with HIV and their parents."

Luc Montagnier, the French doctor who co-discovered HIV, testified in the first trial that the virus was active in the hospital before the Bulgarian nurses began their contracts there in 1998.

The death sentences from the first trial were overturned by the Libyan supreme court, which said there were "irregularities" in the arrests and interrogation of the accused.