Seven Spanish tourists and two Yemeni drivers were killed on Monday when a suicide bomber rammed his explosives-laden car into their convoy at an ancient temple in Yemen, officials said.
The interior ministry said the bombing in the restive northeastern region of Marib appeared to be the work of the al-Qaeda network.
"Preliminary information indicates that the al-Qaeda organisation
is behind the cowardly attack," an interior ministry official told the Saba 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."
It was one of the deadliest bombings targeting foreigners in Yemen, the ancestral homeland of al-Qaeda leader Osama bin Laden which has been battling a number of attacks by the network in recent years.
Witnesses said the attack occurred as the tourists were wrapping up a tour of a temple in Marib which dates back 3000 years to the time of the biblical Queen of Sheba.
There was no immediate claim of responsibility.
The security official said on the website of the Yemeni defence ministry's newspaper that the bomber slammed his explosives-laden vehicle into the tourists' five-car convoy, which included a police car.
In Madrid, an official had said earlier that six Spanish tourists had been killed and seven others injured in the attack.
Witnesses said the blast took place around 6pm (0100 AEST) in a western suburb of the town of Marib, 170 kilometres east of the capital Sanaa.
Tribal sources said it was heard as far as 20 kilometres away from the site of attack, near the Mahram Bilquis, or temple of the moon god.
Yemen has faced a wave of Islamist unrest among its Sunni Muslim majority which it has been fighting with help from US special forces based over the Bab al-Mandab strait in Djibouti.
In October 2000, 17 US sailors were killed when suicide bombers attacked the destroyer USS Cole off the southern Yemeni port of Aden in an attack claimed by al-Qaeda.
In October 2002, a similar attack against the French tanker the Limburg killed one Bulgarian crew member and wounded 12 others.
Thirty-six Yemenis are currently on trial charged with planning and carrying out attacks for al-Qaeda but several are on the run after tunnelling out of a Sanaa prison in February last year and are being tried in absentia.
Last month, a soldier with "emotional problems" opened fire on oil workers with US energy giant Occidental Petroleum killing an Indian woman engineer and wounding six other people, including the local American
boss, in the eastern Shabwah province.
In September 2006, four bombers and a security guard were killed when Yemeni security forces foiled suicide bombings against two oil refineries. In March 2003, a Canadian was killed and another wounded after a Yemeni gunman opened fire at an oilfield east of Sanaa.
Yemen, which has 20 million inhabitants, is one of the world's poorest countries, despite its proximity to oil-rich Saudi Arabia.
The country has also been plagued by frequent kidnappings of Westerners, although all but one have been carried out by tribes with grievances against the central government and the hostages have been released unharmed.
Yemen has also faced a deadly uprising among the Zaidi minority in the mountains on the Saudi border although a ceasefire brokered by the gas-rich emirate of Qatari took effect last month.
In November 2002, a Hellfire missile fired from a US predator drone killed six al-Qaeda suspects in the Marib region, one of them a leading suspect in the sinking of the USS Cole.
It was the first strike outside Afghanistan
of the so-called US war against terror.