Forces of Yemen's embattled president Ali Abdullah Salih fired on unarmed demonstrators elsewhere in the capital, killing scores, wounding hundreds and sparking international condemnation.
The protesters, joined by soldiers from the renegade 1st Armored Division, stormed the base Monday without firing a single shot, according to witnesses and security officials.
Some carried sticks and rocks. They used sandbags to erect barricades to protect their comrades from the possibility of weapons fire from inside the base, but none came and the Republican Guards eventually fled, leaving their weapons behind.
Although the base was not particularly large _ the Republican Guards have bigger ones in the capital and elsewhere in Yemen _ its capture buoyed the protesters' spirits and signaled what could be the start of the collapse of President Ali Abdullah Saleh's 33-year-old regime.
"It was unbelievable," said protester Ameen Ali Saleh of storming the base on the west side of the major al-Zubairy road, which runs through the heart of Sanaa. "We acted like it was us who had the weapons, not the soldiers." "Now the remainder of the regime will finally crumble," said another demonstrator, Mohammed al-Wasaby. "Our will is more effective than weapons. The soldiers loyal to Saleh just ran away." As clashes continued into the night, several loud explosions rocked Sanaa, and a mortar hit the Islamic University of Al-Iman, killing one and injuring two others.
The cause of the explosions was not known.
Saleh went to Saudi Arabia for medical treatment after a June attack on his Sanaa compound and has not returned to Yemen, but has resisted calls to resign.
A final showdown may well pit the Republican Guards, led by Saleh's son and heir apparent Ahmed, against the soldiers of the 1st Armored Division, another elite outfit that has fought in all of Yemen's wars over the past two decades, and their tribal allies in the capital.
The Republican Guards and the Special Forces, also led by the president's son, have long been thought to be the regime's last line of defense against the seven-month-old uprising.
The storming of the base capped two days of clashes in the capital that have left at least 50 people dead and nearly 1,000 injured, mostly demonstrators.
Government forces used snipers stationed on rooftops, anti-aircraft guns, rocket propelled grenades and mortars against the unarmed protesters. Witnesses and security officials described scenes of mutilated bodies, some torn apart. An infant girl, a 14-year-old boy and three rebel soldiers were among the at least 23 people killed on Monday.
"It is over," concluded protest leader Abdul-Hadi al-Azzai. "The Ali Abdullah Saleh regime is finished. How can you negotiate while massacres are ongoing? The world is silent." The head of doctors' syndicate, Abdel-Qawi al-Shemmari, said that two medics were shot to death while trying to rescue the injured. A news cameraman, Hassan Wadah, was in a coma after he was shot in the face, according to witnesses.
The Yemeni Interior Ministry said in a statement that two members of security forces and three citizens were killed, without referring to protesters.
The violence led authorities to close Sanaa's airport and order four flights to go instead to the southern port city of Aden, according to an airport official, who spoke on condition of anonymity because he was not authorized to speak to the press.
But even Aden did not escape bloodshed. Three protesters were wounded in clashes with government forces, witnesses there said.
In the southern city of Taiz, at least four protesters were killed and 40 others were wounded Monday in clashes between anti-regime demonstrators and security forces, according to witnesses.
The latest violence was born partly out of frustration after Saleh shattered hopes raised by the U.S. last week that he was about to relinquish power. The United States once saw Saleh as a key ally in the battle against al-Qaida, but withdrew its support for him as the protests gained strength.
Much is at stake in Yemen for the United States, its Gulf Arab allies, particularly Saudi Arabia, and the West.
Yemen is close to the major oil fields of the Gulf region and overlooks key shipping lanes in the Red and Arabian seas. It is home to one of the world's most dangerous al-Qaida branches, whose militants have staged or inspired a series of attacks on U.S. territory. Already, the chaos in Yemen has allowed al-Qaida militants to capture and hold a string of towns in the nearly lawless south of the country.
Monday's events could significantly help the protesters' cause against the regime, but it is also likely to push Yemen toward civil war or to break up along tribal or regional lines.
The clashes coincided with a flurry of diplomatic activity designed to resolve the crisis.
U.N. envoy Gamal bin Omar and Abdullatif bin Rashid al-Zayani, secretary-general of a regional alliance that groups Yemen's six Gulf Arab neighbors, were in Yemen on Monday. Saleh and King Abdullah, the Saudi monarch, met in the Saudi capital of Riyadh.
"The situation is tense. It can't continue like this.
This is a sign of deep crisis," bin Omar told The Associated Press.
Opposition figures refused to meet the envoys.
"We can't talk after all the bloodshed, the torn limbs and the killing of our people. Any talks would be a collaboration in the crimes committed by the regime," said Mohammed al-Sabri, an opposition spokesman.
U.N. Secretary-General Ban Ki-moon strongly condemned "the excessive use of force by government security forces against unarmed protesters" and called on all sides "to exercise utmost restraint and desist from provocative actions," U.N. spokesman Martin Nesirky said.
The U.S. Embassy said it regretted the bloodshed and called on all parties to "refrain from actions that provoke further violence." Yemen's foreign minister, Abubakr al-Qirbi, said the government was committed to political reforms, but rejected claims of excessive force by police and pro-government militia, accusing some opposition groups of terrorist activity.
Troops from the Republican Guards and the 1st Armored Division were engaged in skirmishes for most of Monday.
"I have been hearing heavy explosions and gunshots since morning," said Atiaf Alwazir, a 31-year-old blogger from Sanaa. Soldiers from the 1st Armored Division soldiers, she said, returned fire, giving pro-regime forces "an excuse to shoot at peaceful protesters." The 1st Armored Division, along with its commander, mutinied and joined the protesters about six months ago.
Its mutiny was followed by a series of high-profile defections that left the president largely isolated but did not weaken his resolve to stay in office.
Last Thursday, the U.S. State Department raised expectations by predicting Saleh would relinquish power within a week under a Gulf-mediated, U.S.-backed deal that would grant him immunity from prosecution in return for stepping down. But violence flared anew after Saleh said he had asked Vice President Abed Rabbo Mansour Hadi to negotiate further.
Saleh has already backed away three times from signing the deal, and many believe this move is the latest of many delaying tactics.