SANAA, Yemen -- Troops commanded by relatives of Yemen's outgoing president attacked a crowd of more than 100,000 protesters peacefully marching into the capital Saturday, killing at least nine and driving the president to promise to leave the country.
Yielding to pressure to defuse the country's turmoil, president Ali Abdullah Saleh said Saturday he would leave for the United States after forces overseen by his son and nephew opened fire on the protesters.
They had marched for four days and 200 miles on foot to pressure the government not to give Saleh immunity from prosecution, in the first march of its kind in the impoverished nation that is home to a dangerous al-Qaida offshoot. After protesters arrived at the southern entrances to the capital, forces of the elite Republican Guard fired on them with automatic weapons, tear gas and water cannons, sparking hours of clashes.
The violence illustrated the confusion in Yemen caused by the slow-motion exit of Saleh from power after 33 years of rule.
After entrenching for months against massive protests across the country demanding his ouster, the president signed a deal in late November handing over his powers to the vice president and committing to leave office in return for immunity.
But Saleh retains his title and remains in the presidential palace, lauded as "his excellency the president" by state media controlled by his supporters.
Opponents say he has continued to wield influence through his relatives and loyalists who still hold powerful positions, undermining Vice President Abed Rabbo Mansour Hadi. That has raised fears that Saleh was looking for a way to continue to rule, even as a national unity government prepares for presidential elections set for February.
The Republican Guard forces, led by Saleh's son Ahmed, and Central Security troops, led by his nephew, have defied orders from Hadi that they pull back from positions in the streets of the capital, even up to a Saturday deadline.
Saleh had been expected to leave Yemen soon after he signed the U.S.- and Saudi-backed accord, ostensibly to undergo treatment for wounds suffered in an assassination attempt in June. But officials say he has stalled on leaving.
Hours after the fighting erupted in Sanaa, Saleh told reporters at his palace that he would leave "in the coming days" for the U.S.
"Not for treatment, but to get out of sight and the media to calm the atmosphere for the unity government to hold the presidential election," he said.
He said he would eventually return and pursue "political work as an opposition figure."
Government officials said ambassadors from the five permanent members of the U.N. Security Council had been in contact with Saleh in the past week to pressure him to leave. The officials spoke on condition of anonymity because they were not authorized to talk to the press.
There was no immediate confirmation from American officials that Saleh would come to the U.S., though Yemeni officials said he had received a visa.
The protesters, who have been massing by the millions around the country since February, oppose an accord for Saleh's exit because it would grant him immunity and because it keeps many of his regime figures in place.
Saturday's "March of Life" demanded Saleh be put on trial for the killings of protesters during his crackdown on the uprising. The crowds marched from Taiz, a city that has been a major opposition center 170 miles (270 kilometers) to the south of Sanaa.
The marchers Saturday were trying to pass down a main avenue where the presidential palace is located when they were met by Republican Guard and Central Security forces, backed by tanks. Troops fired on the crowd, who responded by throwing stones.
The fighting stopped after several hours when the loyalist forces allowed the protesters to continue their march into Sanaa. Amid the clashes, Hadi issued orders for the troops to step aside, but government officials said they only obeyed after international ambassadors contacted Saleh's son Ahmed.
The officials spoke on condition of anonymity because they were not authorized to discuss the behind-the-scenes efforts.
At least eight protesters, including a woman, were killed and more than 200 injured, including 61 wounded by gunfire, according to two doctors at a protesters' field hospital, Mohammed el-Qoutbi and Sadeq el-Shogaa.
In all, at least 500,000 protesters had joined the march by the time it reached Change Square, according to activists. A smaller group broke away and marched on the presidential palace, where troops opened fire on them, killing a ninth protester and wounding four more, activist Abdel-Karim el-Khaywani said.
The violence sparked Prime Minister Mohammed Basindwa to ask a committee to investigate.
"The prime minister called on the Defense and Interior ministers to create an investigative committee into what happened and how protesters were killed," said Information Minister Ali el-Emrani. "The results of the investigation will be shown to the prime minister for the correct course of action."
A human rights organization appeared to lay responsibility on Saleh and the new unity government.
"The shooting of peaceful demonstrators by forces under the control of President Saleh and his top commanders is further proof that promises of immunity encourage rather than deter illegal attacks," Letta Tayler, Human Rights Watch Yemen researcher, said in a statement Saturday.
"Systematic or widespread unlawful killings, carried out as a state policy, are likely to be crimes against humanity," she added.
Even if Saleh carries out his promise to leave, his loyalists remain in place. The unity government is split between opposition parties and Saleh's Congress Party, which holds the powerful defense, oil and foreign affairs ministries. A military committee that Hadi heads to manage military affairs also includes the Congress Party.
There is also confusion over when Saleh is supposed to formally leave as president.
According to the deal signed Nov. 23, the parliament was supposed to convene 29 days later to approve immunity for Saleh; on the next day, he would step down. But parliament has not formally taken up the issue. Some lawmakers say that the "mechanisms" for the deal give them until the February presidential election to grant immunity.
Parliament convened for the first time Saturday since March but did not discuss immunity. Instead it discussed the program of the national unity government, headed by Basindwa, a veteran independent politician. The body can not take action by majority vote; it must reach consensus between Congress Party lawmakers and the opposition.
In past weeks, Saleh loyalists have repeatedly worked counter to Hadi.
Foreign Minister Abu Bakr al-Qirbi, a veteran of Saleh's regime, rejected a U.N. request to send a human rights fact-finding team to Yemen, without consulting with Hadi. When he learned about the incident, Hadi gave his approval.
Last week, the Military Committee ordered the removal of the top military commander in Taiz for the killings of protesters there. But the governor of Taiz, a Saleh loyalist, did not carry out the order.