Thousands of residents were fleeing the Yemeni capital on Friday as deadly clashes between dissident tribesmen and loyalist troops raged for a fourth straight day leaving bodies littering the streets.
Yemeni anti-government protesters shout slogans during a demonstration calling for the ouster of President Ali Abdullah Saleh in Sanaa amid heavy fighting in the city.
The headquarters of national airline Yemenia were burnt down in fierce fighting through the night, an AFP correspondent reported.
The offices of Suhail TV, a channel controlled by pro-opposition tribal chief Sheikh Sadiq al-Ahmar, were also destroyed.
After a brief lull at dawn, artillery and heavy machine-gun fire again rocked the Al-Hassaba neighbourhood of northern Sanaa where Ahmar has his base, witnesses said.
Three shells also struck near the university campus in the city centre where opponents of veteran President Ali Abdullah Saleh have been holding a sit-in since late January.
Troops loyal to dissident General Ali Mohsen al-Ahmar were deployed to protect the few dozen protesters still braving the fighting to camp out in Change Square, witnesses said.
Positions held by the rebel army units also came under artillery fire.
There was no immediate word on casualties from the latest fighting as medics said ambulance crews were unable to access the battlegrounds.
More than 60 people have now been confirmed killed in the fighting in the capital since a fragile truce collapsed on Tuesday between Ahmar's heavily armed tribesmen and troops loyal to Saleh.
Thousands of Ahmar's clansmen were headed to the capital from the countryside to join the fighting, tribal sources said.
An advance party clashed with loyalist troops on Thursday when it was stopped at a military post 15 kilometres (nine miles) north of the capital.
Saleh, who has been in power in Sanaa since 1978, has faced nationwide protests against his rule for the past four months.
Ahmar, who heads one of the impoverished Arabian Peninsula nation's two main tribal confederations, threw his weight behind the protesters in March.
When Saleh last month refused to sign a plan brokered by Yemen's wealthy Arab neighbours in the Gulf for him to step down in return for a promise of immunity from prosecution, Ahmar's fighters seized a string of public buildings across the capital sparking clashes with troops loyal to the president.
A truce announced last week lasted just four days before clashes resumed with each side blaming the other.
A government spokesman on Thursday raised the possibility that Saleh might finally give in to international pressure and sign up to the transition plan drawn up by the six-nation Gulf Cooperation Council.
"The date for the signing will be set soon based on consultations and coordination between Yemen and the Gulf Cooperation Council states," the official Saba news agency quoted the spokesman as saying.
The Senegalese president's office said late Thursday that Saleh had asked President Abdoulaye Wade to approach France and the United States in a bid to arrange a truce followed by elections in Yemen in which Saleh would not stand.
"President Saleh requested President Wade's intervention with France, the United States, Saudi Arabia, the United Arab Emirates and other countries to create the conditions for an immediate ceasefire and the programming of free and transparent elections whose results he pledges to accept," the office said.
Saleh "said he did not intend to stand in these elections", in the telephone conversation with Wade, who is chairman of the Organisation of the Islamic Conference.
In Yemen's second city Taez, south of Sanaa, activists planned fresh protests Friday a day after demonstrators took to the streets, for the first time bearing weapons.
Loyalist troops smashed a long-running sit-in in the centre of Taez earlier this week, leaving more than 50 protesters dead, according to the UN human rights office.
Nationwide, more than 200 demonstrators have been killed since the protests first erupted, according to an AFP tally based on reports from medics.