The people were mourning the deaths of 35 protesters who were shot on Friday, a hospital official said. Many people were shot in the head and chest. The hospital was overwhelmed and people were streaming to the facility to donate blood.
Moammar Gadhafi's regime has been cracking down on protesters who are demanding that he step down and implement democratic reforms.
Before Saturday's violence, Human Rights Watch had estimated at least 84 people have been killed.
Government forces also wiped out a protest encampment and clamped down on Internet service throughout Libya.
Meanwhile, in Tripoli, a counter rally was organized in support of Gadhafi, who's been in power for 42 years.
The Associated Press contributed to this report.