Fresh clashes broke out on Tuesday between Yemeni police and backers of a powerful opposition tribal chief, who have taken over several government buildings in the capital Sanaa, witnesses said.
Fighting between the police and tribesmen loyal to Sheikh Sadiq al-Ahmar which left six people dead on Monday began again early on Tuesday in Al-Hasaba neighbourhood in northern Sanaa, the witnesses said.
Gunbattles continued sporadically near Ahmar's home as several government buildings including the trade and industry ministry remained under his supporters' control, according to witness reports.
Saleh on Sunday warned of civil war in the deeply tribal country as he refused to ink a Gulf-brokered accord under which he would cede power within 30 days in exchange for immunity from prosecution for himself and his aides.
Sources close to Ahmar said the fighting broke out on Monday after security forces tried to deploy around the tribal leader's residence and his gunmen retaliated.
Ahmar said in a statement that five of his supporters were killed Monday and 52 others were wounded.
State news agency Saba said one policeman was killed and five others wounded.
Ahmar, who heads the Hashid tribal federation, the largest in Yemen and a former crucial source of Saleh's power, in March pledged his support for the opposition.
Yemen's opposition vowed on Monday to step up street protests, while insisting on efforts to avoid violence.
Since late January, security forces and armed Saleh supporters have mounted a bloody crackdown on protests demanding his ouster, killing at least 181 people, according to a toll compiled from reports by activists and medics.