More than 50 protesters have been killed in the Yemeni capital, Sana'a, over the past two days in the deadliest crackdown on pro-democracy demonstrations since they began in January.
The resurgence in violence came as envoys from the United Nations and the Gulf Co-operation Council were attempting to negotiate a handover of power from President Ali Abdullah Saleh. Tens of thousands of protesters had taken to the streets in the preceding days in frustration over Mr Saleh's refusal to step down.
Government forces reportedly killed 30 people yesterday, raising the death toll to 56 over two days. One witness reported that a baby girl was killed by a stray bullet.
Following the attacks, thousands of protesters armed with sticks and backed by armed military defectors overran a base of the elite Presidential Guards yesterday. The protesters, joined by soldiers from the 1st Armoured Division, stormed the base without firing a single shot and seized a large number of firearms left by fleeing Guards. "It was unbelievable," said protester, Ameen Ali Saleh, of the storming the base on the west 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."
An opposition source told Reuters last night that anti-government fighters had agreed a ceasefire after the battles, but this was not officially confirmed. The fall of the base into protesters' hands is a significant development in the uprising against President Saleh. Together with the country's Special Forces, the Presidential Guards have long been thought to be the regime's last line of defence.
The storming of the base capped two days of clashes in the capital that, as well leaving many dead, has left nearly 1,000 people injured, mostly demonstrators.
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 those killed yesterday. Protest leader, Abdul-Hadi al-Azzai, said: "It is over. The Ali Abdullah Saleh regime is finished. How can you negotiate while massacres are ongoing? The world is silent."
The violence led authorities to close Sanaa airport and order four flights to go instead to the southern port city of Aden, according to an airport official.
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 wounded, according to witnesses.
The United States, European Union nations and others on the UN Human Rights Council used a meeting of the Geneva-based body to urge the government of Yemen to stop exercising force against peaceful protesters and to seek a resolution to the unrest.
The Foreign Secretary, William Hague, said: "The responsibility for preserving law and order, respecting the right to peaceful protest and ensuring early justice for the victims of yesterday's attacks, rests with the government of Yemen."
Also speaking at the human rights council, the Yemeni Foreign Minister, Abu Bakr al-Kurbi, condemned the killing, adding: "The government will investigate and hold accountable all those who were in charge of these acts."
The latest violence was born partly out of frustration after Mr Saleh, who is recovering in Saudi Arabia from a June assassination attempt, shattered hopes raised by the US last week that he was about to relinquish power.
Diplomats and Yemeni politicians scrambled yesterday to speed up a long-stalled transition plan under which Mr Saleh would hand over power. He has backed out of signing a deal a number of times and many believe the move is a delaying tactic.
A source in Yemen's political opposition told Reuters they were meeting with government officials and diplomats to try to push through a deal.