Pressure is increasing on the regime of Libyan leader Muammar Gaddafi, with reports that hundreds of people have been killed in the unrest.

Libyan Deputy Foreign Minister Khalid Kayem has denied reports by British Foreign Secretary William Hague that Colonel Gaddafi has fled to Venezuela.

There are also reports that protestors have taken control of several cities, including Benghazi, Tobruk and Sirte.

At least 220 people have been killed in six days of unrest.

Al-Jazeera is reporting that military aircraft have bombed many locations in the capital Tripoli.

A resident of the city told the television station: 'What we are witnessing today is unimaginable. Warplanes and helicopters are indiscriminately bombing one area after another. There are many, many dead.'

Col Gaddafi's son said the air raids targeted ammunition depots and not populated areas.

Army units are reported to have defected and two fighter jets have landed in Malta, with the pilots reportedly seeking asylum.

A group of army officers has issued a statement urging fellow soldiers to 'join the people' and help to remove Col Gaddafi from power.

Several Libyan diplomats have already resigned, including the country's deputy ambassador to the UN.

Col Gaddafi has led Libya since 1969 when he headed a coup against the monarchy.

Violence 'must stop immediately' - Ban

A UN spokesman said Secretary General Ban Ki Moon had an extensive discussion with Colonel Gaddafi today.

The spokesman said Mr Ban condemned the escalating violence and told Col Gaddafi it 'must stop immediately'.

US Secretary of State Hillary has called on the Libyan government to respect the rights of its people.

'We join the international community in strongly condemning the violence in Libya. Now is the time to stop this unacceptable bloodshed,' she said in a statement

British Prime Minister David Cameron described the violent crackdown as 'completely appalling and unacceptable'.

He said: 'I call on them even at this late stage to stop. People's aspirations for greater democracy, for greater freedom, for greater rights should be met with reform not repression.'

European foreign ministers have met in Brussels to discuss the escalating crisis.

They issued a declaration condemning the 'ongoing repression against demonstrators in Libya', and called for an immediate end to the use of force.

The Department of Foreign Affairs is advising Irish nationals against all travel to Libya.

The US has ordered all 'non-emergency personnel' to leave Libya and warned US nationals to avoid travel to the country.

Colonel Gaddafi will fight a popular revolt to 'the last man standing', one of his sons said, after protests broke out in the capital for the first time following days of unrest in Benghazi.

Col Gaddafi's son, Saif al-Islam Gaddafi, appeared on national television in an attempt both to threaten and calm people, saying the army would enforce security at any price.

'Our spirits are high and the leader Muammar Gaddafi is leading the battle in Tripoli, and we are behind him as is the Libyan army,' he said.

'We will keep fighting until the last man standing, even to the last woman standing ... We will not leave Libya to the Italians or the Turks.'

He blamed Libyan exiles for inciting the violence, but he also promised dialogue on reforms and wage rises.

Oil prices have soared above $105 per barrel and the Fitch agency downgraded Libya's debt rating a notch from BBB+ to BBB.

BP said it was preparing to move some staff from Libya, which holds Africa's biggest oil reserves.

French oil giant Total said it was repatriating most of its expatriate employees and their families.

Meanwhile, representatives of the Libyan Community in Ireland handed a letter to the Department of Foreign Affairs today urging the Government, the EU and the UN to stand by the people of Libya.

The group says Colonel Gaddafi and his aids have 'the blood of Libyans on their hands' and they should be prosecuted in the international courts.

Libyans living in Ireland staged two demonstrations in Dublin over the weekend.