TRIPOLI, Libya - Muammar Gaddafi's forces battled rebels on several fronts in a worsening of Libya's crisis on Friday and unrest erupted in the capital when gunmen fired to break up crowds shouting "Gaddafi is the enemy of God".
Paris-based Interpol delivered a global alert against Gaddafi and 15 members of his inner circle to help police around the world enforce U.N. sanctions aimed at ending turmoil in the world's 12th largest oil exporter.
Vowing "victory or death", eastern-based rebels pressed home a westwards push towards Gaddafi's Tripoli stronghold with an attack on the oil town of Ras Lanuf, which lies on a strategic coastal road, claiming to have taken its airport.
In the west, security forces loyal to Gaddafi launched an offensive to retake Zawiyah, a town near the capital that has for days been defying his rule, and residents said 30 civilians had been killed. Among the dead was the town's rebel commander.
The rebellion in Zawiyah -- the closest rebel-held territory to the capital and also the site of an oil refinery -- has been an embarassment to the authorities who are trying to show they control at least the west of the country.
The government had said earlier the week it was not using military force to retake rebel-held cities although one official did not rule it out if all other options were exhausted.
Eastern regions of the country, around the city of Benghazi, have already spun out of Gaddafi's control after a popular revolt against his four decades of rule. The rebels' grip on the coastal highway appears to be strengthening.
The uprising against Gaddafi, the bloodiest yet against a long-serving ruler in the Arab world, has knocked out nearly 50 percent of the OPEC-member's 1.6 million barrels of oil per day output, the bedrock of its economy.
The upheaval is causing a humanitarian crisis, especially on the Tunisian border where tens of thousands of foreign workers have fled to safety. But an organised international airlift started to relieve the human flood from Libya as word spread to refugees that planes were taking them home.
The rebels earlier told Reuters they were open to talks only on Gaddafi's exile or resignation following attacks on civilians that have provoked international condemnation, a raft of arms and economic sanctions and a war crimes probe.
"Victory or death ... We will not stop until we liberate all this country," Mustafa Abdel Jalil, head of the rebel National Libyan Council told supporters of the two-week-old uprising.
Abdullah al-Mahdi, a rebel spokesman, told Al Jazeera opposition fighters would attack the capital once a "no-fly" zone was enforced by international powers to try to shatter Gaddafi's grip on the country of six million people.
Western nations have called for Gaddafi to go and are considering various options including the imposition of a no-fly zone, but are wary about any offensive military involvement.
In developments likely to raise concern about dwindling food and medical supplies in rebel-held areas, reports from around the vast country suggested a sharp worsening of a conflict that the West fears could trigger a mass refugee exodus to Europe.
In the east, rebels were attacking a military base on the outskirts of Ras Lanuf, an oil port on the Mediterranean, which has a refinery, pipelines and a terminal, and the army responded with artillery fire and helicopters firing machine guns.
An oil facility at Zueitina, south of the Libyan rebel-held city of Benghazi, has been damaged and was on fire, Al Jazeera said, showing a video of black smoke rising from an oil plant.
In Zawiyah, about 50 km (30 miles) west of the capital, pro-Gaddafi forces fought for hours with rebels who have been holding the town centre, two residents told Reuters.
"From 11 a.m. until now Gaddafi's mercenaries, mainly from Africa, have been opening fire on people here," said a local man called Ibrahim. "Hundreds of victims are now in the town hospital."
"We have no choice but to continue our fight against this dictator."
In Tripoli, shooting rang out across Tajoura district as Gaddafi loyalists broke up a crowd of protesters seeking an end to his long rule and shouting "Gaddafi is the enemy of God!"
The demonstrators spilled out of the Murat Adha mosque after Friday prayers, and several hundred of them began chanting for an end to Gaddafi's four decades in power.
"This is the end for Gaddafi. It's over. Forty years of crimes are over," said Faragha Salim, an engineer at the protest in Tajoura.
Up to 100 people in Tripoli had been arrested, accused of helping the rebels, Al Jazeera said.
Earlier on Friday, rebel volunteers said a rocket attack by a government warplane just missed a rebel-held military base which houses an arsenal in the eastern town of Ajdabiyah.
U.S. President Barack Obama said he was concerned a bloody stalemate could develop between Gaddafi and rebel forces but gave no sign of a willingness to intervene militarily. "Muammar Gaddafi has lost the legitimacy to lead and he must leave," Obama said.
As international efforts progressed to isolate the Libyan leader, Austria widened an asset freeze list to include a top official at the Libyan Investment Authority, Mustafa Zarti, because of possible ties to Gaddafi's inner circle.
Zarti, 40, will be questioned by Austrian authorities on Friday, interior ministry spokesman Rudolf Gollia said.
Zarti told Austrian radio he had no clue how much money the Gaddafi clan might have amassed in the Alpine republic.
Libya's main sovereign wealth fund, the LIA, controls about $65 billion. It worked to enhance Libya's credibility on the international stage by acquiring stakes in European blue-chip firms including Italian bank UniCredit and British publisher Pearson, owner of the Financial Times.
Additional reporting by Maria Golovnina, Yvonne Bell and Chris Helgren in Tripoli, Tom Pfeiffer and Alexander Dziadosz in Benghazi, Souhail Karam and Marie-Louise Gumuchian in Rabat, Yannis Behrakis and Douglas Hamilton on Tunisia border; Christian Lowe and Hamid Ould Ahmed in Algiers; Writing by William Maclean; Editing by Giles Elgood