The violence Saturday began at dawn with intense shelling of the Hasaba district, home to tribal chief Sheikh Sadeq al-Ahmar who opposes Saleh, where explosions were heard throughout the day and into the evening.

Intense street battles followed between troops loyal to Saleh and rival forces throughout the capital Sanaa, leaving at least 20 people dead, and dozens of others wounded, according to the latest tally by medics and government officials.

Medics said at least four of the casualties were civilians, including an employee of the private Yemeni TV channel Saida.

They added that at least six armed tribesmen loyal to Sheikh Sadeq were also killed in Saturday's violence.

A government official, speaking on condition of anonymity, told AFP five pro-Saleh soldiers were killed and dozens of others were wounded in battles with armed tribesmen and rival forces loyal to dissident General Ali Mohsen al-Ahmar who defected in March.

The general and tribal chief, once staunch allies of Saleh, have declared their support for the nation-wide anti-government protests that erupted in January.