Libya rebels fear for Gaddafi prisoners
Libyan rebels say they are concerned over the fate of thousands of prisoners held in Tripoli by the Gaddafi regime.
Rebel military spokesman Col Ahmed Omar Bani said almost 50,000 people arrested in recent months were unaccounted for.
The rebels believe they may be being held in underground bunkers, which have since been abandoned.
Rights groups have seen evidence that dozens of people have been massacred near prisons, but Col Bani did not accuse anyone of killing the prisoners.
"The number of people arrested over the past months is estimated at between 57,000 and 60,000," he said in a news conference in Benghazi.
"Between 10,000 and 11,000 prisoners have been freed up until now... so where are the others?"
The colonel appealed for anyone with information to come forward, and said it would be "catastrophic" if they had been killed.
The BBC's Jon Leyne in Benghazi says many rebels and their supporters were detained by fighters loyal to fugitive leader Col Muammar Gaddafi during the struggle for Benghazi and other cities.
He says many other activists - and even those just suspected of supporting the revolution - were arrested in waves of security crackdowns, particularly when Col Gaddafi was trying to stop the revolution from spreading to Tripoli.
Human Rights Watch has said it has evidence that pro-Gaddafi forces killed at least 17 prisoners and carried out "suspected arbitrary executions of dozens of civilians, including professionals" in the days before Tripoli fell to the rebels.
Reuters news agency claimed earlier this week to have discovered an apparent massacre site in Tripoli; and separately about 50 charred corpses were found in a warehouse south of the capital on Saturday.
But it was unclear who was responsible for any of the killings.
The rebels stormed Tripoli earlier in the week and took control of almost all of it after two days of fighting.
Although sporadic gunshots could be heard in the capital on Sunday, the rebels say they are now in control and are trying to restore basic utilities such as water supply.
However, Gaddafi loyalists are continuing to fight in other parts of the country - particularly around Col Gaddafi's hometown of Sirte.
Mohammed al-Fortiya, rebel commander in Misrata, told AFP news agency that opposition forces were within 30km (18 miles) of Sirte from the west and had captured the key town of Bin Jawad, 100km to the east.
Some rebel commanders believe Gaddafi and his inner circle are likely to have fled to Sirte.
But other rumours swirling around include allegations that the Gaddafis are hiding in Tripoli; that some of them fled to Algiers; or that some have already taken refuge in Europe.
Over the weekend, a spokesman for the Gaddafi regime offered to open talks with the rebel government, the National Transitional Council.
But the NTC rejected the offer, describing the colonel as a criminal who should be put on trial.
UK Foreign Secretary William Hague described the offer of talks as "delusional".