TRIPOLI – Protesters on Monday overran several Libyan cities and Tripoli was rocked by violence some residents said was a "massacre," as the pillars of Moamer Kadhafi's hardline four-decade rule began to crumble.
A suggestion in Brussels by British Foreign Secretary William Hague that Kadhafi may have left the country for Venezuela was swiftly denied by Caracas, home to the embattled Libyan leader's firebrand ally President Hugo Chavez.
Tripoli also denied it, with Deputy Foreign Minister Khaled Kayem telling state television: "The leader is in Libya, as are all the government officials."
The uprising spread to the capital itself, with gunfire rattling Tripoli, where protesters attacked police stations and the offices of the state broadcaster, Kadhafi's mouthpiece, and set government buildings ablaze.
Residents of two districts in Tripoli told AFP in Cairo by telephone there had been "a massacre."
"What happened today in Tajura was a massacre," one said. "Armed men were firing indiscriminately. There are even women among the dead."
Another witness in Fashlum said helicopters had landed what he called African mercenaries who opened fire on anyone in the street, causing a large number of deaths.
Two Libyan fighter pilots -- both colonels -- flew their single-seater Mirage F1 jets to Malta and said they had defected after being ordered to attack protesters in Benghazi, Maltese military and official sources told AFP.
Malta is the closest European state to Libya, just 340 kilometres (211 miles) north of its coastline.
Italy put all military air bases on maximum alert after the fighters landed, ANSA news agency reported, and Prime Minister Silvio Berlusconi said he was "alarmed" by clashes in the former Italian colony.
NATO Secretary General Anders Fogh Rasmussen called on Tripoli to stop the deadly crackdown, saying in a statement: "I am shocked by the indiscriminate use of violence against peaceful protesters in Libya."
Several Libyan diplomats at the United Nations joined calls for Kadhafi to quit, US media reported, with deputy ambassador Ibrahim Dabbashi telling CNN Kadhafi has "declared war" on the Libyan people and is committing "genocide."
In an interview with BBC World, Dabbashi added: "I think it is the end of Colonel Kadhafi, it is a matter of days, whether he steps down or the Libyan people will get rid of him anyway.
Benghazi, Libya's second city and an opposition stronghold in the east, fell to anti-regime demonstrators after military units deserted, the Paris-based International Federation for Human Rights (IFHR) reported earlier.
UN chief Ban Ki-moon told Kadhafi in a phone call that the violence "must stop immediately" and called for a broad-based dialogue, a UN spokesman said.
French President Nicolas Sarkozy also condemned the "unacceptable use of force" and called for an "immediate halt" to the violence.
British Prime Minister David Cameron, on a surprise visit to Libya's eastern neighbour Egypt, where long-time president Hosni Mubarak was swept out on February 11 by a tide of people power, also slammed the violence.
"The violence, the brutality, that has got to stop, that is completely unacceptable," he told Britain's ITV news.
The 27-nation European Union urged all sides to show restraint.
Britain's Hague said earlier Kadhafi may be en route to Venezuela, citing "information that suggests he is on his way," but a Venezuelan official who asked not to be identified retorted: "It's not true."
US President Barack Obama was "considering all appropriate actions" as Washington ordered all non-essential staff out of Libya and warned Americans to avoid travel to the north African country.
Libyan state television said security forces were battling "dens of terrorists" in a sweep that has killed a number of people, without specifying where or who was being targeted.
State television reported that Kadhafi's son, Seif al-Islam, had set up a commission to probe "the sad events," and that it would include "members of Libyan and foreign rights organisations."
He had already appeared on television early Monday to warn of looming civil conflict.
"Libya is at a crossroads. If we do not agree today on reforms... rivers of blood will run through Libya," he said.
"We will take up arms... we will fight to the last bullet. We will destroy seditious elements. If everybody is armed, it is civil war, we will kill each other... Libya is not Egypt, it is not Tunisia."
IFHR head Souhayr Belhassen said protesters controlled Benghazi, Sirte, Tobruk in the east, as well as Misrata, Khoms, Tarhounah, Zenten, Al-Zawiya and Zouara, closer to the capital.
The IFHR said that besides soldiers and diplomats, other senior regime officials had also defected, demanding that Kadhafi step down after more than 41 years in power.
It said the protests had resulted in up to 400 deaths. Human Rights Watch earlier cited a death toll of 233.
Heavy gunfire erupted in central Tripoli and other city areas for the first time since the uprising began in eastern Libya, witnesses and an AFP journalist reported.
"It's definitely the end of the regime. This has never happened in Libya before. We are praying that it ends quickly," one resident of east Tripoli told AFP in Cairo by telephone.
Libya's justice minister, Mustapha Abdeljalil, resigned in objection to "the excessive use of force" against demonstrators, the Quryna newspaper website reported.
In Cairo, Libya's Arab League envoy said he too had stepped down to "join the revolution." Tripoli's ambassador to Delhi also quit, as did a diplomat in Beijing, Al-Jazeera television reported.
Oil prices soared above $105 per barrel on the turmoil, and the Fitch agency downgraded Libya's debt rating a notch from BBB+ to BBB.
British and French energy giants BP and Total were also evacuating some staff from Libya, which holds Africa's biggest oil reserves, as other European governments and firms also scrambled to evacuate their citizens.