SANAA - Yemeni tribes backing a nine-month protest movement against President Ali Abdullah Saleh clashed with his loyalists on Monday in Sanaa, witnesses said, after weekend gunfights left more than 20 dead.

The firefight in north Sanaa began after midnight and continued into the morning in al-Hassaba neighbourhood, the base of tribesmen led by Sheikh Sadeq al-Ahmar, a fierce foe of Saleh, residents said.

A source close to Ahmar said that two of his tribesmen were killed overnight in a bombing carried out by the president's forces, while 13 others were wounded.

Twenty people were killed on Saturday in clashes between between Saleh's loyalists and dissident troops led by General Ali Mohsen al-Ahmar and tribesmen led by Sheikh Sadeq in northern Sanaa.

The clashes erupted in the wake of a non-binding UN Security Council resolution urging Saleh to immediately sign a Gulf-brokered deal to step down.

Meanwhile, a seven-years-old girl was killed and her mother was wounded when a rocket hit their house in the Saawan neighbourhood in northeast Sanaa, which is relatively calm, witnesses said.

Women protesters planned to march in the afternoon from Sanaa's Change Square, the epicentre of anti-Saleh protests, organisers said.

The demonstration would go to Sitin Street but would remain within the area controlled by the dissident First Armoured Brigade, led by general Ahmar, in an apparent bid to avoid provoking Saleh loyalists.

In other unrest, an armed man from tribes backing the protest in the flashpoint city of Taez was killed in dawn clashes with forces loyal to Saleh, a tribal source said.

Armed confrontations between rival forces and militias have escalated in past weeks, raising fears that Saleh's continued refusal to resign will push impoverished Yemen to all-out civil war.

In south Yemen, two soldiers were killed and four others wounded when unidentified gunmen opened fire overnight at a military installation in Al-Muala, in the province of Aden, a wounded soldier said.

South Yemen was independent from the 1967 British withdrawal from Aden until the region united with the north in 1990. The south seceded in 1994, sparking a short-lived civil war that ended with it being overrun by northern troops.

The regions of former South Yemen had seen a large wave of attacks against government forces as southern separatists demanded secession from the north.

But those demands appear to have been put on the back burner since protests broke out in most of Yemen in January demanding the ouster of Saleh.

Al-Qaeda's local branch is also active in the lawless southern and eastern regions of Yemen, and is believed to be taking advantage of the weakening of central authority.