Sanaa, Yemen - Clashes between Yemeni soldiers and armed tribesmen in a mountainous region north of the capital killed at least 40 people on Thursday, a military official said.
The fighting in the Arhab region is one example of the wider security collapse across Yemen since the outbreak of a massive uprising seeking to topple President Ali Abdullah Saleh six months ago.
Armed tribesmen are battling security forces in Arhab, the southern city of Taiz and elsewhere, while militants believed to be linked to al-Qaeda have overrun entire towns in the impoverished country's restive south.
The US and Yemen's powerful Gulf Arab neighbours worry that al-Qaeda and other militant groups will exploit the security vacuum in Yemen to step up operations.
Thursday's clashes northeast of Sanaa's international airport began when tribesmen attacked a base belonging to the Republican Guard, said Sheik Hamid Assem of the Arhab tribe. The elite unit responded by shelling and bombing tribal positions, Assem said, killing and injuring a number of civilians, though he was unsure how many because the battle was still happening.
A military official in Arhab said 17 soldiers had been killed in the fighting and that the troops had seen the bodies of at least 23 dead tribesmen. The official spoke on condition of anonymity under military protocol.
Yemen's Defense Ministry blamed opposition parties and army units that have defected to the anti-Saleh camp for the attack.
Hamid said only tribesmen took part.
Mutual animosity between the tribe and President Saleh has turned violent since the start of the uprising against Saleh's regime six months ago.
The tribe has previously tried to prevent troops from entering the capital, Sanaa, where it feared they would attack protesters.
Elsewhere, security forces and armed government loyalists fired on anti-government demonstrators in the southeastern coastal city of al-Shahr, killing one and injuring three, a resident said on condition of anonymity for fear of government reprisals.
The demonstrators were protesting shortages of fuel and foodstuffs. - Sapa-AP