A prison riot in Sanaa left two inmates dead and three guards injured, a Yemeni security official said on Friday.
Inmates staged a demonstration to protest poor treatment, but it turned violent after police tried to disperse the crowd by using water cannons and tear gas, he said.
Two other inmates were also injured, the official said, speaking on condition of anonymity because he wasn't authorized to talk to the media.
Meanwhile, tens of thousands of people took to the streets across the country demanding that outgoing President Ali Abdullah Saleh be put on trial, activists across the country said.
Saleh was guaranteed immunity from prosecution as part of a U.S.-backed deal signed last month, which allows him to step down after 33 years in power.
Incoming Prime Minister Mohammed Basindwa announced on Wednesday that he had formed a national unity government composed both of Saleh allies and opponents to take over control of ministries.
But the deal is likely to leave more of the current regime intact than the uprisings in Tunisia, Egypt and Libya, and supporters and opponents continue to clash throughout the country.