Seven people were killed in clashes between Yemeni tribal gunmen and suspected al Qaeda fighters on Sunday in Marib province, east of the capital Sanaa, tribal sources said.

Al Qaeda guerrillas killed one tribesman, the sources in the province said, and a later clash between the two sides killed another two tribesmen and four militants.

"The al Qaeda members are the ones who started the attack," a tribesman told Reuters. There was no immediate word on what lay behind the flare-up.

The Yemeni-based al Qaeda in the Arabian Peninsula (AQAP) emerged as one of the network's most aggressive branches, and a direct threat to the United States, when it claimed responsibility for an attempt by a Nigerian man to down a Detroit-bound airliner on Dec. 25, 2009, with a bomb concealed in his underwear.

Maintaining stability in impoverished Yemen is a priority for Washington and Gulf states because of its location next to major oil shipping routes and neighbouring Saudi Arabia, the world's top oil exporter.

A Yemeni official said the government had boosted security in the southern provinces where many of Yemen's oil and gas facilities are located after at least 31 soldiers and police were killed by suspected al Qaeda militants on Friday.

The official told Reuters that about 150 soldiers and private security men trained to fight armed insurgents had been sent to the provinces of Shabwa and Hadramawt.

The official said 15 al Qaeda fighters had been killed since Friday's attacks, but did not elaborate.

In Friday's raids, 21 soldiers were killed when two car bombs exploded at a military camp in al-Nashama, near the coast, Yemen's Supreme Military Council said, and 10 police were killed by gunmen in the inland town of Mayfaa.-Reuters