Sporadic machinegun fire rang out for the third day in the sandbagged streets around the mansion of an influential tribal leader who has backed protesters seeking to overthrow the longtime ruler after repeated international mediation failed.
Black smoke rose from the compound of Sadiq Al-Ahmar, at the center of the clashes that have killed more than 40 people since Monday, when his guards first exchanged fire with loyalist forces they accused of stockpiling weapons at a nearby school.
Authorities closed Sanaa airport and flights were being diverted after clashes broke out with tribesmen loyal to Ahmar, a security official told Reuters, adding that some airlines had begun canceling flights to Yemen on Tuesday.
"What happened was a provocative act to drag us into civil war, but it is limited to the Ahmar sons. They bear responsibility for shedding the blood of innocent civilians," Saleh told selected media including Reuters.
"Until this second, they are attacking the Interior Ministry. But we don't want to widen the confrontation," he said. "They have chosen this and they made the wrong decision to confront the state with this kind of violence." Four people were killed and 11 wounded, the defense ministry said, blaming Ahmar's men. Witnessess and officials said Ahmar's backers took over several ministry buildings near his compound.
The fighting, the most sustained clashes in Sanaa since protests against Saleh's rule began in February, erupted on Monday, a day after the president refused at the last minute to sign a Gulf-brokered deal that would ease him out of power.
Saleh has backed out twice before, but Sunday's turnabout, after loyalist gunmen trapped Western and Arab diplomats in the United Arab Emirates embassy for hours, appeared to have sparked a major reaction.
General Ali Al-Mohsen, a regional army commander who has sided with protesters, called on the armed forces to defy Saleh.
"Beware of following this madman who is thirsty for more bloodshed," Mohsen said in a statement.
Both sides blamed each other for the violence, which the opposition said could start a civil war. The bloodshed dimmed prospects for a political solution to a popular revolt inspired by protests that swept aside the leaders of Egypt and Tunisia.
"I think there's a real risk that violence can escalate, and we see a move toward low intensity civil war," said Shadi Hamid, analyst at the Brookings Doha Center.
"There's a real loss of faith in the political process after Saleh refused to sign a deal several times. That really cast doubt on whether Saleh has any real commitment to letting go of power voluntarily," he added.
Saleh said the deal remained on the table, despite his repeated failure to sign: "I am ready to sign within a national dialogue and a clear mechanism. If the mechanism is sound, we will sign the transition of power deal and we will give up power." "No more concessions after today," he said.
In the capital Sanaa, fighters in civilian clothes roamed the streets in some districts and sporadic bursts of machinegun fire punctuated the air.
Long lines of cars snaked out of the city, bags piled high on their roofs, even as gunmen blocked entrances to prevent tribesmen from bringing in reinforcements, witnesses said.
The situation calmed slightly in the afternoon as mediators tried to seal a truce. Yet in the neighborhoods close to the fighting, men fled with suitcases and women carried their babies in the streets, seeking safety elsewhere.
"It's no longer possible to stay in Sanaa. The confrontations will reach all parts of the city," said Murad Abdullah as he left by car. "I am afraid for my life. I will go to my village in Ibb. The situation there is safe." 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 avert any spread of anarchy that could give the global militant network more room to operate.
UN Secretary Genera Ban Ki-moon's spokesman Martin Nesirky said Ban was deeply troubled by the clashes in Sanaa and called for further peace efforts and an immediate end to the fighting, while Britain reiterated calls on Saleh to sign the exit deal.
But a peaceful outcome looked ever less likely.
Witnesses and officials said supporters of Ahmar, head of the Hashed tribal federation to which Saleh's Sanhan tribe also belongs, were controlling several ministry buildings near the Ahmar compound including trade and tourism, as well as the offices of the state news agency Saba.
Ahmar's fighters had also attacked the headquarters of the interior ministry, the courtyard of which came under fire from rocket-propelled grenades, witnesses said.
Televised images of the Ahmar compound showed tribesmen rushing through opulent but dusty halls, their floors spattered with blood, as they helped colleagues wounded in the fighting.
"This is an attempt to drag the revolution from its peaceful path," opposition politician Hamid Al-Ahmar, brother to Sadiq Al-Ahmar, said on Al Jazeera television.
"But this is understood, and it won't affect the path of the revolution. The popular revolution."
