Eight high-ranking Libyan army officers appeared in Rome on Monday saying they were part of a group of as many as 120 military officials and soldiers who had defected from Libyan leader Muammar Gaddafi's side.
The five generals, two colonels and a major spoke at a hastily-called news conference organised by the Italian government.
An officer who identified himself as General Oun Ali Oun said killing, genocide and violence against women had taken place.
"No wise, rational person with the minimum of dignity can do what we saw with our eyes and what he asked us to do."
Another officer, General Salah Giuma Yahmed, said Gaddafi's army was weakening day by day, with the force reduced to 20% of its original capacity.
The defectors said they escaped Libya over its western border into Tunisia via crossings controlled by the rebels.
Libyan UN ambassador Abdurrahman Shalgam, who has also defected, said all 120 military personnel were outside Libya now but did not say where they were.
Earlier, Al Arabiya television said 120 Libyan officers had arrived in Rome. The Libyan ambassador to Rome, another defector, said only the eight present at the news conference were in the Italian capital.
Italy is one of a handful of countries that has recognized the Libyan rebel movement fighting Colonel Gaddafi as the legitimate representative of the Libyan people.