Twelve Shiite rebels and eight tribesmen died in a battle for control of the predominantly-Sunni provincial capital Ibb which the rebels overran earlier this week, local government officials told AFP.
Explosions were heard across the city as the rebels, known as Huthis, came under rocket-propelled grenade fire from tribesmen in the surrounding countryside, witnesses said.
The fighting came after hundreds of armed tribesmen demonstrated outside the governor's office in the city last evening demanding the withdrawal of the rebels.
The rebels clashed with Al-Qaeda militants overnight in Baida province further east, leaving "dozens" of casualties, tribal and security sources said.
The rebels have clashed repeatedly with Al-Qaeda in the province since Tuesday.
The Sunni extremists have vowed to resist the Shiite rebel advance in the impoverished country, which is located next to oil-rich Saudi Arabia and key shipping routes in the Gulf of Aden.
Rival groups are seeking to exploit a power vacuum in impoverished Yemen, which has been in political deadlock since the rebels took control of the capital Sanaa on September 21.
