Libya's highest judicial body has commuted to life in prison the sentences of six foreign medics who have been on death row for infecting children with the AIDS virus, an official said.

"The Judicial Council decided to commute the death sentence to life in prison," said the source, who spoke on condition of anonymity.

The five Bulgarian nurses and a Palestinian doctor, who has been granted Bulgarian citizenship, could serve out their sentences in Bulgaria, as the two countries have an extradition treaty. It was not immediately clear if the six would be sent to Bulgaria.

However, the Bulgarian chief prosecutor will initiate on Wednesday procedures for seeking their extradition, spokesman Kamen Mikhov said. "From tomorrow, the prosecutor's office will take steps to activiate the Bulgarian-Libyan extradition treaty," he said. "It is a routine procedure that we have launched immediately in other cases."

Washington and the European Union joined in calling on Libya to send the six medics home. "We urge the Libyan government to now find a way to allow the medics to return home," US State Department spokesman Sean McCormack said.

The European Commission described it as a "relief" while adding that the objective remained "their transfer to the EU as soon as possible." Bulgaria joined the EU in January.

Bulgaria's Foreign Minister Ivaylo Kalfin welcomed Libya's decision. "The decision of Libya's Supreme Judicial Council is a big step in the right direction, but for us the case will be over when our compatriots return to Bulgaria," Kalfin told journalists in the Bulgarian capital, Sofia.

Poor hygiene

The decision came after the children's families dropped their call for the death penalty following a compensation deal worth millions of dollars. "We have renounced the death penalty ... after all our conditions were met," said Idriss Lagha, spokesman for the families. "All the families have received compensation."

The Gaddafi Foundation involved in mediating a resolution to the case that has dragged on for eight years and strained ties with the West, has previously said the compensation amounts to about $1 million per child.

The medics, who have been behind bars since 1999, were convicted of deliberately injecting 438 children in a Benghazi hospital with HIV-tainted blood. Lagha has said the number of victims has risen to about 460 after several mothers were infected. Fifty-six children have since died.

The death penalty had been confirmed by the Supreme Court last Wednesday, sparking renewed international concern over their fate.

Nurses Snezhana Dimitrova, Nasya Nenova, Valya Cherveniashka, Valentina Siropulo and Kristiana Valcheva and doctor Ashraf Juma Hajuj have always pleaded their innocence.

They say confessions were extracted under torture and foreign experts have blamed poor hygiene at the hospital for the AIDS outbreak in Libya's second city of Benghazi on the Mediterranean coast.

Both EU External Relations Commissioner Benita Ferrero-Waldner and Bulgaria's Prime Minister Sergey Stanishev had urged Libya's Judicial Council to make a swift and clement ruling.

Last week, the medics sought "pardon and mercy" from the council, which can uphold, modify or overturn the Supreme Court verdict.

Torture accusations

The Gaddafi Foundation, headed by Libyan leader Muammar Gaddafi's son Seif al-Islam, said the money was paid to the victims' families out of a special Benghazi AIDS fund created in 2005 by Tripoli and Sofia under EU auspices.

Among the victims are eight Palestinians, two Egyptians, two Syrians, two Sudanese and a Moroccan as well as Libyans, according to Lagha.

Last week, Libyan Foreign Minister Abdel Rahman Shalgham said the compensation would be paid by "certain European countries and charitable organisations, and from the Libyan state".

He refused to reveal how much money was already in the fund, except to say it ran into "hundreds of millions of dollars".

The French Le Figaro daily had reported on Saturday that some EU countries could be involved in the compensation but the European Commission, which has already committed €2.5 million to the fund, has denied it played any role in the deal.

The six medics also face defamation charges brought by a senior police officer over their torture accusations, although this case could also be resolved.