SANAA, Yemen - The U.S.-backed president of Yemen suffered a devastating political blow on Sunday when his own powerful tribe demanded his resignation, joining religious leaders, young people and the country's traditional opposition in calls for an end to his three decades in power.
Massive crowds flooded cities and towns around the impoverished and volatile nation, screaming in grief and anger as they mourned dozens of protesters killed Friday when President Ali Abdullah Saleh's security forces opened fire from rooftops on a demonstration in the capital.
Saleh appeared to be trying to hold on, firing his entire Cabinet ahead of what one government official said was a planned mass resignation, but making no mention of stepping down himself. Yemen's ambassador to the United Nations and its human rights minister had announced their resignations earlier in the day.
Experts said that Saleh, who has cooperated closely with U.S. military operations against his country's branch of al-Qaida, had lost the support of every major power base in Yemen except the military.
Many said he would now be forced to choose between stepping down and confronting demonstrators with even deadlier force.
"We're talking a new set of dynamics that are driving the conflict into either the resignation of Saleh or a very serious clash between the two sides," said Ibrahim Sharqieh, deputy director of the Brookings Doha Center. "The U.S. should work now on an orderly transition in Yemen and press Saleh to find an arrangement that doesn't allow chaos."
Sharqieh said from Washington that it was far from clear what would replace Saleh if he goes. Options could include a military-run transitional government and an administration of traditional political opposition parties.
Sharqieh described the Obama administration as "extremely worried."
Saleh and his weak government have faced down many serious challenges, often forging tricky alliances with restive tribes to delicately extend power beyond the capital, Sanaa. Most recently, he has battled an on-and-off, seven-year armed rebellion in the north, a secessionist movement in the south, and an al-Qaida offshoot that is of great concern to the U.S.
Al-Qaida in the Arabian Peninsula, which formed in January 2009, has moved beyond regional aims and attacked the West, including sending a suicide bomber who came terrifyingly close to blowing up a U.S.-bound airliner with a bomb sewn into his underwear. The device failed to detonate properly.
Yemen is also home to U.S.-born radical cleric Anwar al-Awlaki, who is believed to have offered inspiration to those attacking the U.S., including Army Maj. Nidal Hasan, who is accused of killing 13 people and wounding dozens in a 2009 shootout at Fort Hood, Texas.
"The U.S. just cannot afford losing Yemen," Sharqieh said.
The Yemeni government appeared to shy away from more violence for the moment, disbanding police and special forces around Sanaa University, which has been the center of the deadly crackdown, and replacing them with a largely unarmed force.
"From now on, we will be controlling the entrances and exits of the square by orders from the supreme military command," said Lt. Col. Mohammed Hussein.
Soldiers with sticks checked people arriving to join crowds of thousands who carried the flag-wrapped bodies of the slain through the square where on Friday gunmen hidden on rooftops fired methodically into protesters. Police sealed off a key escape route with a wall of burning tires and more than 40 people, including children, perished, many shot in the head and neck.
The country's chief prosecutor was leading an investigation into Friday's shootings in Sanaa, according to a statement released through Yemen's embassy in Washington. Seventeen people suspected of orchestrating the shootings were being questioned, it said, without identifying them.
The day after the bloodshed, the head of Saleh's Hashed tribe met with religious leaders at his home on Saturday and emerged with a statement of support for the protesters' demands that the president step down.
"We hail with all respect and observance, the position of the people at the (Sanaa University) square," Sheik Sadiq al-Ahmar said late Saturday.
Al-Ahmar does not command the automatic loyalty of tribal members but his positions are deeply influential, Sharqieh said.
The tribal leader now stands with opposition parties who have gone from negotiating Saleh's eventual departure to demanding his immediate resignation.
The parties said they would not be satisfied by Saleh's pledges not to run for re-election in 2013 or to hand power to his son.
"Our only choice now is the removal of the regime soon. We stand by the people's demand," opposition leader Yassin Said Numan told The Associated Press.
The opposition will under no circumstances agree to a dialogue with Saleh after Friday's violence, spokesman Mohammad al-Sabri told The Associated Press.
"The president must understand that the only way to avoid more bloodshed and strife in this country is for him to leave. Nobody will have any regrets about him," he said.
The president has now been left almost entirely dependent on external support, mainly from the United States, which sends Yemen hundreds of millions of dollars in military aid to battle the potent al-Qaida offshoot in the country's mountainous hinterlands, political analyst and researcher Abdelkarim al-Khiwani said.
The U.S. has condemned violence against Yemeni protesters.
People living in apartment buildings around the square tossed down flowers at Sunday's funeral procession. Electricity was cut off for about three hours in Yemen's major cities, and activists accused the government of trying to block people from seeing television coverage of the march. Cell service was also interrupted.
Massive crowds flooded into the Sanaa University square and solidarity demonstrations were held across the country in regions including Aden, Hadramawt, Ibb, Al-Hudaydah, Dhamar and Taiz.
Human Rights Minister Huda al-Ban said she was stepping down to protest the government's "horrible, coward and perfidious crime." And a Foreign Ministry official told The Associated Press that U.N. Ambassador Abdullah Alsaidi had sent in his letter of resignation.
He was replaced later Sunday. The Cabinet that Saleh fired will remain as a caretaker government until a new one is formed.
Health Minister Abdul-Karim Rafi told reporters the killing of protesters was "a crime unacceptable by logic or could be justified."
He said 44 protesters were killed and 192 wounded, 21 critically.
Prosecutor-General Abdullah al-Ulty said that 693 protesters were hurt and some bodies have not yet been identified.
Mohammed Naji Allaw, a lawyer and activist, said the government offering money to victims' families to not cooperate with the investigation, and was pressuring them not to participate in the funeral procession.