Massive demonstrations were reported in five cities but protesters haven't turned out in large numbers in the country's capital of Tripoli, the BBC reported Friday.
Thousands of protesters demonstrated overnight in Benghazi, Libya's second-largest city, and activists set up camps in al-Bayda, witnesses said.
Supporters of Libya's government demonstrated in Tripoli, shouting slogans backing Libyan leader Moammar Gadhafi.
Human Rights Watch, which listed the number of dead in Libyan protests at 24, urged authorities to stop using lethal force unless absolutely necessary and to open an independent investigation into the killings.
"The security forces' vicious attacks on peaceful demonstrators lay bare the reality of Moammar Gadhafi's brutality when faced with any internal dissent," Sarah Leah Whitson, HRW's Middle East and North Africa director, said in a statement posted on the organization's Web site. "Libyans should not have to risk their lives to make a stand for their rights as human beings."
Activists had used social networking Web sites such as Facebook and Twitter to call for a "Day of Rage" on Thursday.
One protester told the BBC he witnessed the deaths of three demonstrators in al-Bayda.
"The police are using their guns. ... I have a video, which shows the police shooting people, but the government has blocked the Internet in al-Bayda. We are asking the authorities to unblock the Internet service," the protester said. "The biggest problem now is that doctors are not treating the injured and so they die. It's a crime."
In Benghazi, a woman told the British broadcaster she saw hundreds of demonstrators participating in the rallies and that police fired their guns in the air and into the crowd.
The Middle East has witnessed a wave of protests generated by dissatisfaction about unemployment, living costs, government corruption and leadership. Two of the protests led to the overthrow of presidents -- Zine al-Abidine Ben Ali in Tunisia and Hosni Mubarak in Egypt.