Demands grow for Saleh to face trial despite promises of immunity from prosecution for him and his family [AFP]

At least 12 people were killed, five of them civilians, during violent clashes between forces loyal to Ali Abdullah Saleh, Yemen's president, and dissident tribesmen in the country's second-largest city Taiz, medical and security officials said.

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Witnesses said the fighting erupted before dawn on Thursday as loyalist troops tried to storm the city centre, a stronghold of armed tribesmen who have pledged support to the protest movement against Saleh's 33-year rule.

Security officials said five Yemeni soldiers were killed in battles and medics said that at least seven people, including five civilians, were killed and 30 wounded.

The fighting came as the opposition announced a government of unity would be announced in Yemen before Sunday.

The move is in line with a peace deal that is to see Saleh step down from power.

"There is a deal with the ruling party on the distribution of posts. Forming a cabinet will be very easy," Mohammed Qahtan, spokesman for the parliamentary opposition coalition, told the AFP news agency.

The government will be announced on Friday or Saturday, he added.

During Thursday's clashes troops of the loyalist 33rd Brigade fired artillery rounds at several neighbourhoods of Taiz, a stronghold of the anti-government protests continuing since January, but met strong resistance, residents said.

The heavily armed tribesmen destroyed one army tank stationed near the city's traffic police headquarters, the witnesses added.

Fierce fighting

All roads leading into the city were blocked by the fierce fighting that has left outlying districts isolated from the city centre.

The Yemeni government accuses what it says are "militias from Al-Islah," a religious movement that is the main opposition party in parliament, of being behind the unrest and deploying in residential areas across Taiz.

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On Tuesday, Saleh's forces shelled several neighbourhoods of the city, killing one person and destroying dozens of homes, medics and residents said.

Violence across Yemen has left hundreds dead since the protests erupted. A UN-backed power transfer deal signed by Saleh last month has failed to halt the violence.

The UN Security Council called on Monday for those behind killings and human rights abuses in Yemen to be "held accountable," as demands grow for Saleh to face trial despite promises of immunity from prosecution for him and
his family extended under last month's agreement with the parliamentary opposition.

Source: Al Jazeera and agencies