Opposition forces said they agreed a truce with the government, but several rounds of gunfire and explosions were heard in the Yemeni capital and a government official said the two sides were still working on a ceasefire deal.
The military confrontation between opposition forces loyal to defected General Ali Mohsen and government troops was triggered by the government crackdown on protests, threatening a new and even more violent phase in Yemen's eight-month standoff.
Demonstrators demanding an end to Saleh's 33-year rule ratcheted up their protests on Sunday to try to break a stalemate, and government forces responded with heavy fire, while snipers shot at protesters from rooftops.
At least 30 people were killed on Monday, raising the death toll to 56 over two days. The government reported two deaths among its soldiers on Monday.
Witnesses said government forces had traded heavy rifle and missile fire with troops loyal to Mohsen, who defected following an earlier crackdown in March which killed 52 people.
Several countries including the United States condemned the violence but gave little indication of how they planned to exert pressure on Saleh.
Medics said at least 187 protesters were wounded on Monday after a dramatic escalation in violence which began with a huge anti-government march on Sunday. At least 400 protesters and police have died since the revolt began eight months ago.
The violence on Monday began when troops fired at an area seized by protesters on Sunday night to force them back to Change Square.