The protests against President Ali Abdullah Saleh by the powerful tribes of Yemen left 38 dead on Tuesday as the uprising threatened to turn into a militia-led revolt.

Medical officials said that 24 tribesmen were killed in the fiercest fighting on Sana’s streets. Since the death toll has incresed, President Saleh has called for a cease-fire. In a statement, both sides have been asked to lay down their arms and the tribesmen have been asked to withdraw from government buildings.

Government officials said that 14 soldiers have also been killed and 20 were missing as the situation deteriorated.

The Interior Ministry blamed Sheik Sadeq al-Ahmar, the head of Yemen’s largest tribe Hashid for the bloodshed, while the opposing groups have accused Saleh of “dragging the country to chaos.’’

Both sides blame each other for the latest violence which has caused the rift to deepen. This suggests that Yemen might have to showdown between armed tribal militias and the pro-Saleh troops.

Saleh has refused to step down despite three months of non-stop protests calling for an end to his 32-year rule.

Yemen tribes are considered allies for any government to survive. Ahmar and other tribes had abandoned Saleh two months ago even though he is a member of the Hashid clan.

The tribes had decided to control their responses even as government forces fired on protesters during the attacks that have claimed more than 150 lives.

However, the battles that began on Monday might increase pressure on Saleh’s regime -- either by encouraging more tribes to join the fight or by forcing more military officials to abandon the present government.

Tuesday’s clashes broke out after government forces tried to storm Ahmar’s compound in Sana’s Hassaba district. Militiamen used chains to seal the doors of the ruling party headquarters and several other ministries.