Embattled Libyan ruler Col Muammar Gaddafi's stronghold in the capital Tripoli is tense ahead of possible protests later.
Opponents of his government have reportedly been calling for rallies in the city after Friday prayers.
Fresh air strikes have been launched on rebel-held territory in the east of the country.
The revolt, which broke out in mid-February to end Col Gaddafi's 41-year rule, has shown signs of stalemate.
'Arrests'
There are unconfirmed reports overnight of mosques having been closed, arrests and the internet being shut down.
Protests last week after Friday prayers in several districts of the city were fired on by Gaddafi supporters, witnesses of the shootings have said.
Security forces have reportedly carried out a wave of detentions, killings and disappearances in the city in recent days.
A Libyan warplane bombed the rebel-held coastal town of Ajdabiya on Friday, narrowly missing a munitions dump.
Gaddafi forces also carried out the second air raid in as many days on the key rebel-held port of Brega, home to the country's second largest oil facility, Al Arabiya news network reported.
On Thursday, rebels in Libya's second city of Benghazi said they would not negotiate unless Col Muammar Gaddafi resigned and went into exile.
The National Libyan Council - led by former Libyan Interior Minister Mustafa Abdel-Jalil, who went over to the opposition last month - also called for foreign intervention.
The rebels - a mixture of citizen militias and army defectors armed with machine guns and rocket-propelled grenades - have been securing Brega in anticipation of a fresh onslaught by Gaddafi loyalists.
Several hundred members of the Tuareg community from Mali have joined Col Gaddafi as mercenaries, a senior official from that North African nation told the BBC.
Gaddafi loyalists withdrew west to another oil port, Ras Lanouf, following their defeat in a battle on Wednesday.
The rebels have held funerals for some of the 14 fighters killed in that clash.
The major western rebel-held cities of Zawiya and Misrata have also repelled attacks by Gaddafi loyalists.
Meanwhile, during a White House news conference on Thursday, US President Barack Obama repeatedly said Col Gaddafi should quit.
"Going forward, we will continue to send a clear message: the violence must stop," he said. "Muammar Gaddafi has lost legitimacy to lead and he must leave."
Luis Moreno-Ocampo, chief prosecutor of the International Criminal Court, said Col Gaddafi and his inner circle were under its spotlight.
The court has identified at least nine incidents that could constitute crimes against humanity, including the alleged killing of 257 people in Benghazi last month.
The crisis has spawned a humanitarian crisis, with some 200,000 migrant workers having fled Libya, into Egypt, Tunisia and Niger, according to the International Organization for Migration.