Libyan forces carried out an air strike on the edge of the rebel-held town of Ajdabiya Friday, as opponents of veteran leader Moamer Kadhafi called fresh protests in the capital Tripoli.

Libyan rebels prepare an anti-aircraft gun at the west gate of Ajdabiya, 160 kms west of Benghazi, on March 3.

US President Barack Obama said all options were on the table for driving Kadhafi out of power as the strongman\'s son said air strikes on rebel-held positions were scare tactics rather than to inflict serious damage.

Despite grave reservations expressed by the US military command, Obama said a no-fly zone was among the "full range" of options as he demanded that Kadhafi "step down from power and leave."

Forces still loyal to the veteran strongman, who has ruled the oil-rich North African state for 41 years, have been bombing rebel-held positions in Libya\'s east and thousands of people are desperate to flee the country.

The latest air strike, early Friday, targeted a military base on the edge Ajdabiya, a strategic crossroads, but caused no injuries or damage, rebels said.

"There was a bomb outside the military base near Ajdabiya," said Mohammad Abdallah, a rebel fighter at the last checkpoint of the town on the road to Brega, where rebels fought deadly battles with government forces on Wednesday.

The military barracks on the outskirts of Ajdabiya has been targeted repeatedly by Kadhafi\'s forces since rebels in the east began a popular uprising on February 15 to evict the Libyan leader.

Rebels managed to beat off a dawn attack on Brega on Wednesday in the first real military battle since the start of the uprising. Another bombing raid was carried out early Thursday but caused little damage.

Kadhafi\'s son Seif Al-Islam told Britain\'s Sky News the air strikes were designed only to scare the rebels rather than cause damage, amid reports pilots reluctant to bomb their compatriots were deliberately missing their targets.

"This is the oil and gas hub of Libya," he said, vowing the regime would do all in its power to recapture Brega.

"All of us, we eat, we live because of Brega. Without Brega six million people have no future because we export all of our oil from there."

The patchwork Libyan opposition now controls swathes of eastern and western Libya including the city of Benghazi and some oil installations. Kadhafi remains firmly in control of the capital Tripoli.

Kadhafi\'s tight grip on the capital was to be tested following calls among the opposition to gather for demonstrations after Friday prayers, according to several Facebook and Twitter groups run by Libyans abroad.

Separately there were reports that Libyan state TV had called for protests against any foreign intervention in Libya. There was no immediate confirmation.

Scattered protests were staged in Tripoli on the Muslim day of rest a week ago but security forces opened fire indiscriminately on worshippers leaving mosques, killing several people and wounding dozens.

More than 100,000 people have left Libya to escape the violence, which has killed at least 1,000, according to conservative UN estimates.

The International Criminal Court\'s prosecutor said in The Hague that Kadhafi and key aides would face investigation over alleged crimes against humanity.

"We have identified some individuals with de facto or formal authority, who have authority over the security forces," Luis Moreno-Ocampo told journalists.

"They are Moamer Kadhafi, his inner circle, including some of his sons."

Kadhafi\'s ally President Hugo Chavez of Venezuela joined the diplomatic offensive, proposing an international mediation mission to pull Libya from what Russian President Dmitry Medvedev said was the "verge of civil war".

The Chavez proposal got short shrift from the West, and Libyan rebels in their eastern fiefdom argued that Kadhafi was free to flee to Venezuela if he chose.

"We have a very clear statement. It\'s too late. Too much blood has been spilt," Mustafa Gheriani, a spokesman for the opposition\'s self-declared national council in Benghazi, told AFP.

The rebels would "never negotiate with anybody on the blood of our people", he said.

"The only way we can negotiate with Chavez is if Kadhafi goes to Venezuela (for good). Then we\'ll ask him to have Kadhafi back in Libya to be prosecuted by our justice."

Obama told a White House news conference that Kadhafi\'s "appalling violence" on his own people showed that he had lost all legitimacy.

"Going forward, we will continue to send a clear message: The violence must stop. Moamar Kadhafi has lost legitimacy to lead and he must leave," he said.

Obama said he did not want to be "hamstrung" in his options and confirmed that a no-fly zone was under consideration. Britain and France back the idea, but there are divisions internationally and even within Washington.

Defence Secretary Robert Gates and top US military officials warned Wednesday that imposing no-fly zone would be a major military undertaking, and would necessarily require air strikes to take out Libya\'s air defences.

"Let\'s just call a spade a spade," Gates told US lawmakers, decrying "loose talk" about a no-fly zone.

A major European operation is under way to airlift from Tunisia thousands of people who have fled the bloodshed in Libya, and Obama also offered US planes to repatriate Egyptian refugees.

The Libya disruption has been a factor in driving up world oil prices, along with unrest against authoritarian regimes across the Arab world.

Crude prices resumed their upward path in Asian trade Friday on doubts about Venezuela\'s proposal to mediate in the crisis in oil-rich Libya, analysts said.

New York\'s main contract, light sweet crude for delivery in April, or West Texas Intermediate, rose 12 cents to $102.03 per barrel.

Brent North Sea crude for April delivery gained 12 cents to $114.91.

In Sunni-controlled Saudi Arabia, the world\'s top oil exporter, cyber activists called for a "Day of Anger" on Friday in the country\'s eastern Shiite-majority region, following the arrest of a Shiite cleric.