Violence across Yemen has left hundreds dead since anti-government protests erupted in February [Reuters]

At least three people have been killed in the Yemeni city of Taiz, activists and medical workers said, as thousands gathered for an anti-government rally in the city.

Residents blamed the deaths on government troops, saying tanks had shelled Taiz from the surrounding mountains
on Friday for a fourth straight day.

Twelve people were killed in the city during violent clashes between forces loyal to outgoing President Ali Abdullah Saleh, and dissident tribesmen on Thursday, officials said.

Mohammed Basindwa, a former foreign minister designated by opposition parties to lead a government to be split between them and the outgoing President Ali Abdullah Saleh's party, said his side would rethink its commitment to that deal if the killing in Taiz did not cease.

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In a statement, Basindwa said the killing was "an intentional act to wreck the agreement".

Elsewhere in the country, thousands filled city centres on Friday in the capital Sanaa and the city of Lib, demanding Saleh be prosecuted for the killings during Yemen's nine-months long uprising.

Saleh, 69, has ruled Yemen for 33 years and signed a deal mediated by Gulf Co-operation Council states in which he agreed to step down in return for immunity from prosecution for himself and his family.

The opposition said on Thursday that it had agreed the lineup of an interim government, to be announced in the coming days. 

The interim government is supposed to lead Yemen towards a presidential election that Abd-Rabbu Mansour Hadi, the
vice-president to whom Saleh has transferred his powers, has set for February 21.

Violence across Yemen has left hundreds dead since the protests erupted.