At least nine people have been killed and eight injured in a bomb blast at a historical site in Yemen popular with Western tourists.

The explosion occurred around 6:00 pm (1500 GMT) on Monday at the ancient Balqis temple in the town of Marib, 170km east of the capital Sanaa, officials and witnesses said.

Provincial authorities said the blast was caused by a car bomb. Witnesses reported seeing a car arrive at the site before the explosion.

"Preliminary information indicates that the al-Qaeda organization is behind the cowardly attack," an interior ministry official told the Sabam news agency.

"This criminal attack has killed seven Spanish tourists and two Yemeni nationals who worked as drivers and tourist guides, and wounded six Spanish tourists and two [Yemeni] nationals."

Convoy targeted

An official at Spain's foreign ministry in Madrid confirmed the tourists were Spanish nationals.

Witnesses said the attack occurred as the tourists were ending their tour of the temple.

A security official at the Yemen defense ministry said a car filled with explosives hit the tourists' five-car convoy, which included a police car.

No organization has yet claimed responsibility for the bombing.

Security sources said the attack came after al-Qaeda issued a statement demanding the release of fighters from Yemeni jails.

The sources also said al-Qaeda's statement said Sanaa should distance itself from the US.

PHOTO CAPTION

People gather around the aftermath of the explosion in Yemen