Libya is in chaos tonight with anti-government protesters fiercely refusing to be cowed by live firing from the Libyan army and bombing by the Libyan air force in parts of Tripoli.
Barely a week after his Egyptian neighbour Hosni Mubarak was forced from office, Muammar Gaddafi, North Africa's longest-ruling leader sent out a warning that he was ready for a fight to the death, despite signs his grip on power is loosening.
The president of Yemen, another ruler who has chalked up more than three decades in power, also defied calls to quit saying he would only exit if defeated at the ballot box.
And a top exiled opposition figure said he planned to return to Bahrain, fuelling pressure on the ruling royal family for reform.
While there was fresh violence in several Arab cities, the most dramatic events were in Tripoli where heavy gunfire broke out in downtown areas for the first time since the uprising began in eastern Libya last week.
Tripoli residents told AFP by telephone y there had been "a massacre" in the Tajura and Fashlum districts, with indiscriminate shooting and women among the dead.
"What happened today in Tajura was a massacre," one resident said. "Armed men were firing indiscriminately. There are even women among the dead," he said, adding mosque loudspeakers were putting out appeals for help.
Another witness in Fashlum told AFP that helicopters had landed what he called armed African mercenaries in the neighbourhood, who opened fire on anyone in the street, causing a large number of deaths.
Reports that Gaddafi had fled the chaos were denied however by Libyan officials, as well as in Caracas after British Foreign Secretary William Hague said "information that suggests (Gaddafi) is on his way" to Venezuela.
Amid mounting international concern over the eruption of violence, foreign governments and companies scrambled to flee after Tripoli warned of a "fight to the last bullet."
In a rambling national address, Gaddafi's son Sayf al-Islam warned "rivers of blood will run" in a blunt threat of "civil war."
But in a sign of deep cracks developing in the usually closed regime, Libya's deputy ambassador to the United Nations called for Gaddafi to quit, accusing him of "genocide" and saying he should stand trial for war crimes.
"He has to leave as soon as possible. He has to stop killing the Libyan people," Ibrahim Dabbashi told CNN and other hastily convened media at the United Nations in New York.
Although government restrictions have complicated the task of compiling a tally, Human Rights Watch said 233 had been killed since last Thursday while the International Federation for Human Rights (IFHR) put the toll at 300-400.
IFHR head Souhayr Belhassen said several eastern cities, including the second city of Benghazi and Sirte, had fallen to demonstrators after army units formerly loyal to Gaddafi had defected.
Media reports from around the region said Libya's justice minister, Mustapha Abdeljalil, had also resigned along with Libya's Arab League envoy and Tripoli's ambassador to Delhi as well as a diplomat in Beijing.
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.
"It's definitely the end of the regime. This has never happened in Libya before. We are praying that it ends quickly," a Tripoli resident told AFP in Cairo by telephone.
Amid the turmoil, oil prices soared above $105 per barrel, and the Fitch agency downgraded Libya's debt rating a notch from BBB+ to BBB.
British energy giant BP said it was preparing to evacuate some staff from Libya, which holds Africa's biggest oil reserves, and French oil giant Total said it was repatriating most of its expatriate employees and their families.
The United States also ordered all non-essential personnel to leave the country.
Yemen's Ali Abdullah Saleh, the region's second longest-ruling leader, is also clinging to power despite a growing clamour for his departure.
"If they want me to quit, I will only leave through the ballot box," Saleh told reporters.
Tens of thousands of protesters took to Yemen streets Monday, including in the capital Sanaa, the southern city of Aden, the northern city of Saada, the western port of Al-Hudaydah and Taez, in the south.
According to an AFP tally based on reports by medics, 12 people have been killed and dozens more wounded since February 16 when protests first erupted in Yemen against Saleh, who has been in power since 1978.
While Yemen is the poorest Arab country, wealthy states have also been caught up in the wave of unrest.
In Bahrain, thousands of government loyalists thronged a Manama mosque late Monday in support of the Gulf state's monarch.
Thousands of mainly Shiite anti-government protesters were also camping out in the central Pearl Square, after calling for a huge demonstration on Tuesday, to oust the Sunni Al-Khalifa dynasty which has ruled the Gulf kingdom for centuries.
"No mother can keep her children from coming here," Um Alawi, clad in full niqab and flanked by her daughters, told AFP. "Sacrifice is today the duty of all Bahrainis."
Hassan Mashaima, leader of Bahrain's opposition Haq movement, told AFP he would return to Manama on Tuesday, despite the threat of terrorism charges.
As protests raged, the kingdom issued a statement saying it would no longer host the Bahrain Formula One Grand Prix on March 13.