Libyan Justice Minister Ali Omar Hassnaoui said the six may appeal to the supreme court and, if that went against them, to a superior body called the high council of justice.

The six denied the charges and their defense lawyers argued that the children had been infected with HIV due to bad hygiene at the Benghazi hospital before their clients began working at the hospital.

In the wake of the verdict, their lawyers said they planned to appeal against their latest conviction.

The medical workers, who had been detained for nearly seven years, had previously been sentenced to death by firing squad in 2004. But Libya's supreme court quashed the ruling and ordered a retrial following an appeal in December 2005.

Europe and the United States have called Libya to release the defendants, saying that the six were scapegoats for the poor hygiene conditions in the hospital. Bulgaria also contended that the children were infected by unhygienic practices at their Libyan hospital.

Families of the dead children have demanded 15 million dollars in compensation which was rejected by the Bulgarian government, which insists that its nationals are innocent.

"The sentence ... raises some very serious questions and I agree with those who think it is exceedingly cruel," Russian Foreign Minister Sergei Lavrov told a Moscow news conference.

Lavrov said he had already urged the Libyan leadership to show mercy, adding: "I do not know what scope there is in Libyan legislation for saving these people's lives but it goes without saying that I am calling precisely for that."

The medics deny infecting the children, more than 50 of whom have since died.

Bulgaria, the European Union and Amnesty International criticized the verdict on Tuesday. U.S. Secretary of State Condoleezza Rice said she hoped the medics would be allowed to return home at the earliest possible date.

The Russian appeared to have been poisoned with a high dose of polonium 210, but the circumstances surrounding his death have so far baffled British police.

The results of the tests on the Swedes show that one of them has slightly raised levels of polonium.

"In one case it has been possible to see a slight increase of polonium in the urine, but it's not at a level that poses a health risk," said Jonas Holst, a medic at the crisis management unit at the National Board of Health and Welfare.

The person with the increased level of polonium visited the barat the hotel in London where Litvinenko stayed. No treatment is required, said Holst.