Tribal gunmen kidnapped two American tourists in Yemen on Monday and are demanding the release of a jailed tribesman for the pair, U.S. officials have confirmed. 

"The kidnapping has been claimed by a tribal group and is not believed to be terrorism related," U.S. State Department spokesman PJ Crowley said Monday. "At the present time we are working actively with local authorities to gain the release of our two U.S. citizens.

Yemeni security officials, a taxi driver and tribesmen said the two -- a man and a woman -- were seized while traveling in al-Hudaydah province west of the capital San'a.

The officials spoke on condition of anonymity because they were not authorized to speak to the media.

Taxi driver Mohammed Saleh, who was driving the two, said six gunmen stopped them on the road and took them to the al-Hamra village. Al-Sharda tribesmen said the hostages were now "guests" in the village.

Kidnappings are endemic in Yemen and are usually carried out by disgruntled tribesmen hoping to win concessions from the government. In the past few years, however, Al Qaeda has begun kidnapping foreigners as well, often with lethal results.

They often take place outside the heavily guarded capital, underlining the fragility of security in rural areas. It is this weak government authority outside San'a that's believed to have tempted Al Qaeda militants to seek refuge in the impoverished Arab nation in the southern corner of the Arabian Peninsula, thus posing a threat to the interests of the West and its allies in a strategic part of the Middle East.

The United States and other Western powers have been increasing their support to Yemen's security forces to enable them to better deal with the Al Qaeda threat. However, such efforts are often frustrated by the protection offered by tribal chiefs to the militants, the country's difficult mountainous terrain and the deep anti-Western sentiments shared by many Yemenis.

"There has been, unfortunately, a bit of a side business in what are called tourist kidnappings, where for whatever reason a certain tribe has a particular grievance with the government and uses the presence of foreigners for leverage," Crowley said. "We have every reason to believe that this is once of those cases." 

The Associated Press contributed to this report