More than 40 Yemenis were killed in pitched street battles in the capital today as fighting aimed at ending president Ali Abdullah Saleh's three-decade-long rule threatened to ignite civil war.
Residents were fleeing Sanaa by the hundreds, hurriedly fastening possessions to the roofs of cars, hoping to escape the violence that has killed more than 80 people since Monday.
The fighting, pitting the security forces of president Ali Abdullah Saleh against members of the country's most powerful Hashed tribe led by Sadiq al-Ahmar, was the bloodiest Yemen has seen since protests began in January. The battles threatened to spread into other parts of the capital Sanaa.
The defence ministry said 28 people were killed in an explosion in an arms storage area of Sanaa at dawn today.
Fighters in civilian clothes roamed some districts today and machinegun fire rang out sporadically.
Sporadic explosions could be heard in the capital near the protest site where thousands of people demanding Mr Saleh to leave after nearly 33 years in power are still camped.
Black smoke from mortar fire mixed with a haze of pollution and dust that hangs over Sanaa like a shroud.
The United States and Saudi Arabia, both targets of foiled attacks by a wing of al-Qaeda based in Yemen, have tried to defuse the crisis and stem any spread of anarchy that could give the global militant network more room to operate.
There are worries that Yemen, already teetering on the brink of financial ruin, could become a failed state that would undermine regional security and pose a serious risk to its neighbour Saudi Arabia, the world's biggest oil exporter.
At a meeting in Deauville, France, leaders of the G8 powers called on Mr Saleh to quit, keen to avert civil war inflaming one part of the Arab world as they prepared to help new democracies flourish in another.
"We deplore the fighting that occurred overnight which was a direct result of the current political impasse, for which president Saleh has direct responsibility due to his refusal to sign the GCC transition agreement," a French foreign ministry spokesman said, referring to the Gulf Cooperation Council.
For the United States, who long treated Mr Saleh as an ally against al-Qaeda, secretary of state Hillary Clinton said in Paris: "We continue to support the departure of president Saleh who has consistently agreed that he would be stepping down from power and then consistently reneged on those agreements."
Washington ordered all non-essential diplomats and embassy family members to leave Yemen. "The security threat level in Yemen is extremely high due to terrorist activities and civil unrest," the US state department said.
Yemen's state prosecutor ordered the arrest of "rebellious" leaders of the tribal group led by the al-Ahmar family and a government official said the headquarters of an opposition television station had been "destroyed", without giving details.
Tribal leader Mr Ahmar told Reuters there was no chance for mediation with Mr Saleh and called on regional and global powers to force him out before the Arabian Peninsula country of 23 million people plunges into civil war.
"Ali Abdullah Saleh is a liar, liar, liar," said Mr Ahmar, leader of the Hashed tribal federation. "We are firm. He will leave this country barefoot."
Mr Saleh said yesterday he would not bow to international "dictates" to step down and leave Yemen despite mounting protests and international pressure.
With fighting now escalating after a tense but mostly contained standoff between Mr Saleh's supporters and opponents, panic has begun to grip the capital.
There were long queues at Sanaa bakeries, banks and petrol stations as residents tried to stock up on cash and food before fleeing to safer areas in the impoverished state.
Several electronic and clothes shops opened but few buyers were around except those shopping for food.
The most recent clashes have been concentrated in a part of northern Sanaa where fighters loyal to Mr Ahmar have been trying to take over government buildings.
Broken glass, bloodstained corridors and a makeshift clinic for the wounded attested to the damage at Mr Ahmar's mansion, while Sanaa residents heard the sounds of explosions ripping through the city in the midnight hours.
A government official had said the airport was briefly closed due to the fighting but had reopened.
The most recent bout of fighting erupted a day after Mr Saleh pulled out for the third time from a deal mediated by Gulf Arab neighbours for him to quit and make way for a unity government.
Pressure has been mounting since February, when protesters inspired by democratic revolutions in Tunisia and Egypt began camping in squares and marching in their hundreds of thousands to call for Mr Saleh to go. His attempts to stop the protests by force have so far claimed the lives of 260 people.
US president Barack Obama has called for Mr Saleh to sign the deal but analysts said Washington has little leverage in Yemen even though it has sent about $300 million in aid to help prop up Mr Saleh's government.
Mr Saleh said yesterday he would make no more concessions to those seeking his departure. But the capital of the country of 23 million has begun to feel like a city at war.
Witnesses and officials said supporters of Mr Ahmar, head of the Hashed tribal federation to which Mr Saleh's Sanhan tribe also belongs, controlled several ministry buildings near Mr Ahmar's compound including the trade and tourism ministries, as well as the offices of the state news agency Saba.
Mr Saleh told a group of invited reporters including yesterday that his government was "steadfast".
But general Ali al-Mohsen, one of Yemen's most powerful military leaders who defected in March, called on the armed forces to defy the president. "Beware of following this madman who is thirsty for more bloodshed," he said.
At the protest camp, demonstrators voiced concern at the turn of events and what they described as Mr Saleh's readiness to go to civil war rather than quit.
"The Ahmar family are part of the revolution and the president is trying to turn it into civil war," said Ahmed al-Malahi, a 39-year-old medical doctor.
"This president has oppressed us. Imagine with all the resources of Yemen the people live in abject poverty...There is no other people in the peninsula who live under such conditions: poverty, backwardness, unemployment and corruption.
"All the government revenues and all the foreign aid to Yemen are going straight to their pockets."
Most said they were determined to continue their protests because they saw no future for their children under Mr Saleh.
"Saleh has destroyed our country and our youths," said Mohammed al Jaradi, a retired soldier, 50. "He crushed our future and we accepted our lot but we want to save the future of our sons. This is why we will not back down and won't be silenced so that ours sons will have a better future."
Reuters