SANAA (Reuters) - Gunmen abducted three Westerners in the centre of the Yemeni capital Sanaa on Friday, a security official told Reuters.

"People saw a car stop in Tahrir Square, militants snatching three Westerners and speeding away," the official said, adding that police were searching for the kidnappers.

No further details were immediately available about the nationality of the kidnapped or the affiliation of the abductors, but al Qaeda militants and tribesmen have been involved in kidnapping foreigners in the past.

The incident came just two days after President Abd-Rabbu Mansour Hadi overhauled the armed forces in a drive to bring stability and weaken political rivals in the impoverished country.

Lawlessness in Yemen has alarmed its neighbor and top world oil exporter Saudi Arabia, as well as the United States, which increasingly views the Arabian Peninsula state as a front line in its struggle against al Qaeda and its affiliates.

Tribesmen have often carried out abductions to pressure the government to release their kinsmen from prison.

This week's overhaul of the armed forces is widely seen as part of an effort to curb the still considerable influence of former President Ali Abdullah Saleh, loosen his family's grip on the military and implement an internationally-backed plan to restore stability.

Hadi's government is also grappling with the threat of al Qaeda and a growing secessionist movement in the south.

(Reporting by Mohammed Ghobari; Writing by Mahmoud Habboush; Editing by Patrick Graham)