Speaking to the court in Tripoli, Omar Abdulkhaleq, the chief prosecutor in the case called for their execution.
"The act was cruel, criminal and inhuman," he said. "It's a human catastrophe. We demand the death penalty for the accused."
All six defendants, who have spent seven years in jail, were in court where they heard testimony from a young girl who was among those infected.
The retrial, which began on May 11, has heard only from prosecution witnesses so far.
The five Bulgarian nurses and a Palestinian doctor, who worked in a hospital in Benghazi, are accused of having infected 426 children with HIV, of whom 52 have since died of Aids.
The accused were first detained in 1999, and the initial case has put a strain on relations between Triploi and Sofia as the defendants were earlier condemned to death by firing sqad in May 2004.
In December 2005, the supreme court overturned the convictions and sent the case back to a lower court.
About 50 of the HIV-infected children have died, fuelling popular anger in Libya.
Familes of the infected have
protested outside the court
Allegations of torture
The medics have denied the charges in their first and second trials and have repeatedly testified that they were tortured into making confessions.
According to Bulgarian newspaper reports, police officers allegedly forced the nurses to undress before them, put insects on their bodies and set dogs on to them.
The five women were also allegedly kept without water and denied sleep in a tiny cell where they had to urinate in a juice box or a plastic bag. Police officers were also said to have threatened to infect them with Aids, the reports said.
Bulgaria and its allies say the outbreak at the hospital where they worked began before they arrived.
International Aids experts have said that the infections in the hospital were attributable to hygiene problems.
Tripoli has suggested that the nurses could go free if Bulgaria pays compensation to the children and their families, who have demanded 4.4 billion euros [$5.5 billion].
Bulgaria has refused to pay, but has joined the US, the EU and Libya in agreeing to back the creation of an aid fund.