Al Qaeda in Yemen previously focused on high-impact strikes against Western and Saudi targets, but appears now to be targeting government forces in response to enhanced Yemen-U.S. security coordination and a government crackdown.

"Al Qaeda is believed to have been behind the attack on the soldiers' patrol," said a local official who asked not to be named. There were no reports of damage to energy installations in the small oil producer.

Fighting also flared up on July 25 between a pro-government tribe and Shi'ite rebels, hours after the two sides agreed to a truce following battles last week which threatened to reignite a civil war.

Tribal leader Sheikh Saghir Ibn Aziz blamed the rebels, named Houthis after the clan name of their leaders, for the renewed fighting after clashes killed up to 70 people last week.

Al Arabiya television said the fighting, which killed four rebels, broke out after the tribesmen failed to withdraw from a position which the rebels said was part of the truce accords. There was no immediate comment by the rebels on their website.

Last week's fighting, in which government forces were also involved, was the bloodiest in the north since a truce in February ended a war between the state and the rebels that has raged intermittently since 2004 and last year drew in neighboring Saudi Arabia.

Yemen's President Ali Abdullah Saleh called on July 25 for a permanent end to fighting in the north, especially in Saada province, the rebels' stronghold.

"Six wars are enough. Yes to security, stability and peace in Saada. No to the latest war," Saleh said in remarks carried by regional television stations.