ADEN (Reuters) - Armed Yemeni tribesmen on Monday kidnapped a Swiss citizen working for the Red Cross in the southern province of Abyan, a Yemeni security source said.

The aid worker was taken from a vehicle in the city of Jaar where he was travelling with Yemeni co-workers and there had been no demands from the tribesmen, the security source said.

Kidnappings of Westerners in Yemen are mostly carried out by al Qaeda militants or tribesmen.

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

A Swiss woman held for nearly a year in Yemen was freed by her kidnappers and flown to Doha in February following mediation by Qatar. Armed tribesmen had kidnapped the teacher in the western Yemeni city of Hudaida in March 2012 to press the Sanaa government to free jailed relatives, a Yemeni official said.

(Reporting by Mohamed Mushashaf; Writing by Amena Bakr; Editing by Mark Heinrich)