Yemen unrest: 'Dozens killed' as gunmen target rally
The gunmen fired from rooftops overlooking the central square in what the opposition called a massacre.
President Ali Abdullah Saleh declared a national state of emergency but denied his forces were behind the shooting.
US President Barack Obama has condemned the violence, urging Mr Saleh to allow peaceful protests.
In a statement , he said those responsible for Friday's violence "must be held accountable".
Separately, France demanded an end to attacks "by security forces and armed pro-government groups... against people exercising their rights to free speech and demonstration", Reuters reports.
Yassin Noman, rotating president of Yemen's umbrella opposition group, was quoted by Reuters news agency as saying there was "no longer any possibility of mutual understanding" between the protesters and President Saleh, and he should resign.
Another opposition spokesman, Mohammad al-Sabri, accused Mr Saleh of presiding over a "massacre".
"This is part of a criminal plan to kill off the protesters, and the president and his relatives are responsible for the bloodshed in Yemen today," he told the Associated Press news agency.
Soon after the shooting in the capital, the country's Tourism Minister, Nabil al-Faqih, resigned in protest.
A month of violence has gripped Yemen and demonstrators reportedly gathered in other cities across the country on Friday:
- In the city of Taez, security forces, tanks and armoured vehicles surrounded a square where protesters had gathered, and access to the square was blocked
- In Mahweet, protesters reportedly captured five gunmen who had been firing at protesters; they were found inside the governor's house along with weapons and spent ammunition, eyewitnesses told the BBC
- Tens of thousands attended the funeral of a protester in the southern port of Aden, AFP reports; Kazinform cites BBC News.
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