State TV in Yemen has shown pictures of night-time clashes between anti-government protesters and security forces in the capital Sanaa.
Violence has continued in other parts of the country, a day after Yemeni forces killed 13 protesters, raising fears of a wider conflict.
It comes as Qatar pulled out of a Gulf-brokered plan to end the unrest by getting President Ali Abdullah Saleh to quit power. He has refused to sign the deal, which is now said to be on the brink of collapse. The latest attacks on protesters have prompted the US-based Human Rights Watch to call for Saleh’s proposed immunity under the deal to be withdrawn.
Security forces reportedly wounded dozens of demonstrators in the southern city of Taiz. Elsewhere in the south two protesters were killed.
More than 160 people have now been reported killed since the uprising began in late January.