Violence escalates across Yemen amid civil war fears

In the capital, Sanaa, security forces battled tribesmen in the streets after a ceasefire broke down, leaving at least two dead. At least 12 protesters were meanwhile shot dead in Taiz.

And in Zinjibar, Islamist militants killed at least five Yemeni soldiers.

There are fears that the unrest could turn into a civil war.

Western powers and Yemen's Gulf neighbours have been pressing Mr Saleh to sign a deal to hand over power to help end the crisis.

A US state department spokesman on Tuesday urged the president to leave office after 33 years in power "and to move Yemen forward".

In Sanaa, there were fresh clashes between fighters loyal to Sheikh Sadiq al-Ahmar, the powerful head of the Hashid tribal confederation, and government forces still loyal to President Saleh.

The tribesman seized nine government ministries in the al-Hassaba district during fighting in the capital last week which left more than 115 people dead.

They withdrew from one ministry on Sunday as part of a ceasefire agreed with the government. But they accused Mr Saleh of not withdrawing forces surrounding Sheikh Ahmar's compound.

During Tuesday's fighting, the tribesmen seized control of the upper house of parliament, the headquarters of Mr Saleh's ruling General People's Congress party, the interior ministry and a key road leading to the airport.

A spokesman for Sheikh Ahmar said his supporters would seize anywhere which "poses any danger to us and that they are firing at us from".

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