Shelling in Yemen's capital killed five supporters of a powerful opposition chieftain on Tuesday, his tribe said, as clashes intensified between embattled President Ali Abdullah Saleh's security forces and the tribesmen.
In the second successive day of fighting, a source close to tribal chief Sheikh Sadiq al-Ahmar told AFP that "an armoured vehicle stationed near the interior ministry fired shells and killed five people" outside his home.
Machineguns and rocket-propelled grenades were used as fierce fighting between police and tribesmen loyal to Ahmar gripped Al-Hasaba neighbourhood in northern Sanaa where the tribal chief's home and the ministry are located, an AFP correspondent said.
"Two tribesmen were wounded" on Tuesday, another tribal source close to Ahmar said, adding heavy shelling also targetted tribesmen stationed at several government buildings including the trade and industry ministry.
Meanwhile, Yemen state television quoted an interior ministry official as saying that Ahmar's supporters fired grenades at the buildings of the ministries of interior and tourism, as well as the state news agency Saba.
Heavy gunfire was heard near Ahmar's home where tribal dignitaries from Yemen's powerful tribes of Bakil and Hashid had gathered in support of Ahmar.
Most of the dignitaries had insisted on a peaceful solution to end the violence that killed six people Monday, although tribal mediators have so far failed to secure a ceasefire.
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 had broken out on Monday after security forces tried to deploy around the tribal leader's residence and his gunmen retaliated.
But a security official said Ahmar's men broke into a nearby school and police responded.
The accounts could not be independently verified.
Ahmar, meanwhile, accused Saleh, who is facing mounting pressures to quit office after 33 years, of trying to spark a "civil war" in an attempt to remain in power, in a statement received by AFP.
The tribal chief said five of his supporters were killed on Monday and 52 others were wounded. Saba news agency 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.
One of the 10 sons of Abdullah al-Ahmar, who was until his death Saleh's main ally, Sadiq al-Ahmar is capable of rallying some 10,000 armed supporters, according to tribal sources.
Yemen has an estimated 60 million firearms in private hands, roughly three for every citizen.
The country'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.
Analysts warned the crisis may degenerate into a civil war after Saleh refused to sign the Gulf-brokered deal to end the popular uprising inspired by regime-changing movements in Tunisia and Egypt.
Saleh "realises that his regime is over but he is looking for a decent exit," said Ibrahim Sharqieh, deputy director of the Brookings Doha Centre.
"He doesn't want an exit like that of Egypt's Hosni Mubarak or Tunisia's Zine el Abidine Ben Ali. He is basically concerned over the way by which he will be remembered in history."