Security forces in Yemen have killed more than 50 people in two days of violence against anti-government protesters, activists say, in the country's bloodiest clashes for months.
Snipers in Sanaa fired from rooftops at a protester camp, killing bystanders including a child, witnesses said.
Government forces also shelled areas held by troops loyal to the protesters.
The opposition has promised to carry on its campaign to oust President Ali Abdullah Saleh.
For months, thousands of people have been waging a campaign to depose Mr Saleh, who has ruled the country since 1978 and is currently in Saudi Arabia recovering from a bomb attack in June.
The opposition believes the government is deliberately orchestrating the violence to derail any chance of agreement.
But a Yemeni minister strongly denied reports that the authorities had fired on peaceful demonstrators, telling the BBC government forces were being attacked by militants sympathetic to al-Qaeda.
The US and EU nations were among members of the UN Human Rights Council who used a meeting in Geneva on Monday to urge Yemen's government to stop using force against protesters.
Meanwhile, as the violence intensified, envoys from the UN and the Gulf Co-operation Council arrived in Yemen, in a new attempt to negotiate a handover of power from Mr Saleh.
Air attacks
The last two days have seen the worst violence in the country for several months: on Sunday, 26 people were killed and many more injured as they marched towards the presidential palace in Sanaa, the capital.
