The six were found guilty of deliberately infecting hundreds of Libyan children with the deadly HIV virus.
The health workers, detained in Tripoli in early 1999, were convicted of giving 426 Libyan children at a Benghazi hospital HIV, the virus believed to cause AIDS, with contaminated blood products.
The Libyan verdicts give the defendants the right to appeal.
The Bulgarian government condemned the Libyan ruling, and called for a strong reaction from its Western partners the EU, NATO, and the United States.
"I'm shocked by the verdicts. The government's official position is that we are not going to accept them," Justice Minister Anton Stankov, speaking on behalf of the government, told a news conference.
When the health workers were arrested, Libyan leader Colonel Muammar al-Qadhafi had accused them of acting on the orders of foreign intelligence. Libyan authorities claimed the plot was to spread HIV virus among 1000 Libyan children; in order to turn the Libyan people against their government.
The defendants admitted they were linked to foreign intelligence in a police investigation. But they denied the testimonies before the court and said they were extracted from them under duress.
Bulgarian medics were moved
from jail to house arrest in 2002
The Libyan National Security Court refused the case in 2002, saying it did not pertain to national security. The criminal court in Bangazi where the crime was committed, however, accepted it.
The case triggered wide political debate. Bulgaria put pressure on several western states to intervene and convince Qadhafi to release the Bulgarian citizens.
"I'm shocked by the verdicts. The government's official position is that we are not going to accept them"
Anton Stankov, Bulgarian Justice Minister
Bulgarian Foreign Minister Solomon Passy paid several visits to Libya, holding long negotiations with Libyan officials and visiting families of Libyan infected children.
Due to strong pressure on Libyan authorities, a Bulgarian lawyer was allowed to defend the defendants in Libyan court. It was the first time in Libya's history that a foreign lawyer is allowed to proceed before a Libyan court.