Anti-Gaddafi protests staged in Tripoli (VIDEO)

Libyan security forces were reportedly using tear gas to break up anti-government protests in Tripoli on Friday as fighting between rebels and troops loyal to leader Muammar Gaddafi continued across the country.

Hundreds of protesters, some burning flags and others chanting "Gaddafi is the enemy of God," had massed in Tripoli's eastern suburb of Tajoura following traditional Friday prayers, according to witnesses.

Security had been tight around the area with Gaddafi loyalists setting up traffic checkpoints, the BBC reported. Tripoli residents earlier reported constant surveillance, searches by armed militiamen and disappearances of those involved in the now-weekly protests, VOA said.

The New York Times said official minders had ordered journalists not to leave the hotel in Tripoli where they had all been housed. The government says about 130 journalists have been permitted to enter Libya, but Gaddafi had made clear that they were "not popular."

The eastern port of Brega — subjected to airstrikes by Gaddafi's warplanes a day earlier — was reportedly calm Friday, but the anti-government uprising which began in mid-February continued in the country's northwest, with medical staff at a hospital in Misrata saying locals were "trying to protect our city," according to Reuters.

And Libyan rebels reportedly came under air attack for a third day on Friday as Gaddafi tried to loosen the opposition's expanding grip on a key coast road.

A doctor on the northwestern part of the Libyan coast said residents were scrambling to stay safe as attackers shot at doctors and ambulances in Misrata.

"We are are holding our city, we are trying to protect our city," the doctor told Anderson Cooper's "AC360" early Friday. At least 40 people were killed in the city and 300 suffered gunshot wounds to the head and chest, the doctor added.

Air strikes also targeted a military base near the rebel-held town of Ajdabiya on Friday.

Eastern-based rebels spearheading a two-week-old revolt told Reuters on Friday that they were open to talks only on Gaddafi's exile or resignation.

"If there is any negotiation it will be on one single thing — how Gaddafi is going to leave the country or step down so we can save lives. There is nothing else to negotiate," said Ahmed Jabreel, an aide to ex-justice minister who heads the rebel National Libyan Council in east Libya. "We are not going to negotiate any political solution. We want him put on trial, but if we don't give him an exit, we know more people will be killed."

Attacks on civilians in Libya have brought global condemnation and triggered a war crimes investigation by the International Criminal Court.

Obama threatens U.S. intervention

In his most forceful response yet to the escalating crisis in Libya, U.S. President Barack Obama has ordered Muammar Gaddafi to "step down and leave," and signaled that the U.S. military would consider intervening if the situation there deteriorated.

Obama said the United States and the international community were outraged over the violence being committed by pro-government forces and that “Muammar Gaddafi has lost the legitimacy to lead, and must leave.”

He said the country could face a humanitarian crisis if civilians become trapped and in danger or a stalemate becomes bloody.

While Obama on the one hand said he had given the military the "full capacity to act, potentially rapidly," he cautioned his remarks with the need to act in consultation with the international community. He confirmed that a no-fly zone was one option but also emphasized that the preference will be for the Libyans to determine their own destiny.

"The president’s remarks illustrate the dilemma confronting the White House: Libya now looks less like a Facebook-fueled rebellion and more like an African civil war of the kind that the United States has tried to avoid. With forces loyal to Colonel Gaddafi staging a desperate counterattack to seize rebel-controlled cities, Mr. Obama acknowledged that Libya could descend into a bloody stalemate," reports the New York Times.

"In such a situation, there are few realistic — let alone attractive — military options for the United States, which is already entangled in two other wars. Even limited options, like a no-fly-zone intended to prevent Libyan planes from shooting at their own people, are drawing opposition from some European allies, and would be unlikely to win the approval of the United Nations Security Council."

Gaddafi has shown no signs of a willingness to step down and has reportedly increased his demand for mercenary forces. An official from Mali, one of the world's poorest countries, said another 200 to 300 mercenary forces had left for Libya, AP reports.

About 40 cars with prospective fighters from Mali had reportedly crossed into Algeria, but the fighters were worried about continuing into Libya because of opposition forces guarding the border.

Gaddafi forces have locked down the capital Tripoli, where a sense of fear and hopelessness pervades. Residents report disappearances, constant surveillance and beatings by government supporters.

Crimes against humanity

The International Criminal Court announced Thursday that it will investigate Gaddafi, his sons and his inner circle for possible crimes against humanity in the violent crackdown on anti-government protesters.

Prosecutor Luis Moreno-Ocampo said Gaddafi's security forces were alleged to have attacked "peaceful demonstrators" in several towns and cities across Libya since Feb. 15, according to reports.

Moreno-Ocampo said: "We have identified some individuals with de facto or formal authority, who have authority over the security forces" as having command over the forces that may have committed crimes. "They are Muammar Gaddafi, his inner circle, including some of his sons."

He also warned that leaders of the Libyan opposition, who have seized weapons from the Libyan military, could be investigated if allegations were raised against them.

Rebel forces reportedly fought off repeated counteroffensives by Gaddafi's supporters and mercenaries Thursday and successfully reinforced the oil port of Brega.

"Army units that have joined the rebels fanned out in the oil facilities and port at Brega, armed with machine guns and rocket-propelled grenade launchers and dressed in camouflage army uniforms with checkered keffiyehs. They were backed by at least a dozen pickup trucks with mounted machine guns or towing rocket launchers," AP reports.

Watch GlobalPost correspondent Nichole Sobecki's report on the fighting in Brega.

Much of the heightened criticism of Gaddafi comes after he began bombing raids against opposition forces in places like Brega.

But Saif al-Islam, Gaddafi's son, called the bombing raids a "big misunderstanding" designed to scare off rebels.

In an interview with Sky News, Islam said: "First of all the bombs [were] just to frighten them to go away. Not to kill them."

Pop stars "embarrassed" over connections

Meanwhile, celebrities continue to find themselves facing a public relations disaster over their connections to the Gaddafi family. Singers Beyonce and Mariah Carey tried to distance themselves from the rogue family, for whom each performed at glitzy New Year's eve parties, Reuters reports.

Beyonce performed for the family and its entourage at a private party on the Caribbean island of St. Barts in 2009. She said she will donate the money from the party to a charity working in Haiti.

"Once it became known that the third party promoter was linked to the Qaddafi [Gaddafi] family, the decision was made to put that payment to a good cause," according to a statement on her website.

Carey said she felt "horrible and embarrassed" to have performed for the Gaddafi family, and she will donate proceeds from a new song to charity.

Canadian artist Nelly Furtado announced via her Twitter account Monday that should donate the $1 million she received to perform for the family in Italy in 2007. 

— Hanna Ingber Win, Freya Petersen, Barry Neild