The death toll for the worst violence in months rose to nearly 50 in two days of clashes.
The protesters, joined by soldiers from the rebel 1st Armoured Division, stormed the base without firing a single shot and seized a large number of firearms, according to witnesses and security officials.
The anti-government force used sandbags to erect barricades as they advanced, providing their allied troops with the shelter they needed in case they took fire from inside the base. Republican Guards' troops did not fire at the protesters and eventually fled, leaving their weapons behind.
Violence has flared anew in Yemen in frustration after President Ali Abdullah Saleh dashed hopes raised by the US last week that he was about to relinquish power after 33 years of autocratic rule.
At least 23 were killed today and 26 yesterday, almost all of them protesters. Dozens have been wounded.
The fall of the base into protesters' hands is a significant development in the seven-month-old uprising against President Saleh, who went to Saudi Arabia for medical treatment after a June attack on his Sanaa compound and has not returned to Yemen since.
It signals what could be the start of a final showdown between the Republican Guards, led by President Saleh's son and heir apparent Ahmed, and the soldiers of the 1st Armoured 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 and Monday's events could significantly help the protesters' cause against the regime.
The 1st Armoured Division, along with its commander, mutinied and joined the protesters about six months ago, dealing a serious blow to President Saleh's efforts to cling on to power in the face of the popular uprising.
"It was unbelievable," said protester Ameen Ali Saleh of storming the base on the west side of a major road that runs through the heart of Sanaa. "We acted like it was us who had the weapons, not the soldiers."
To other protesters, the fall of the base may signal the near-collapse of the regime.
"Now the remainder of the regime will finally crumble," said another protester, Mohammed al-Wasaby. "Our will is more effective than weapons. The soldiers loyal to Saleh just ran away."
Yemen's protest movement has stepped up demonstrations in the past week, angered after President Saleh deputised Vice President Abed Rabbo Mansour Hadi last week to negotiate further on a Gulf-mediated, US-backed deal under which he would step down in return for immunity from prosecution. Saleh has already backed away three times from signing the deal.
Many believe the move is the latest of many delaying tactics. President Saleh has resisted calls to resign.
Today's killings took to nearly 50 the number of people killed in two days of fighting in Sanaa and elsewhere in the impoverished nation in the southern corner of the Arabian Peninsula. The fighting marked the most serious outbreak of violence in months, as frustration in the streets again builds over the president's refusal to step down.
Security officials and witnesses said hundreds of protesters headed toward the headquarters of the Special Forces in the south of the city. They said the protesters have stopped their advance about 100 yards short of the complex, but it was not immediately clear whether they planned to later storm it too.
The officials said 20 of the 23 killed today were on Sanaa's central Hayel street. They included a child, a 14-year-old boy and at least three 1st Armoured Division soldiers. Mortar shells thought to have been fired by pro-regime forces killed another two people in the capital, said the officials.
Scores of protesters suffering gunshot wounds were taken to hospitals in Sanaa, according to Mohammed al-Maqtari, a doctor at a field hospital set up by the protesters. The wounded included soldiers from the 1st Armoured Division. Witnesses said the soldiers were involved in skirmishes with the Presidential Guards.
Tens of thousands of protesters demonstrated in Sanaa Sunday to press demands for Saleh to step down. Pro-regime snipers and forces using anti-aircraft guns killed at least 26 of the protesters.
The regime's use of violence has drawn fresh condemnation from the West.
The United States, European Union nations and others on the UN Human Rights Council today used a meeting of the Geneva-based body to urge Yemen's government to stop using force against peaceful protesters and seek a resolution to the unrest.
The country'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.
"We have presented evidence proving that many accusation made against security organisation are baseless," Mr al-Qirbi told the meeting on Monday. He also rejected calls for an independent international investigation into the crackdown, saying they were "inconsistent with the recommendations calling for dialogue between Yemeni political parties to solve the crisis."
AP
