Two gunmen shot dead on Sunday a US citizen who worked at a language school in Yemen's second city of Taez, a security official said.
The assailants rode a motorbike in their attack on the man, who was the deputy directer of a Swedish language centre in the city, 270 kilometres (173 miles) southwest of Sanaa, the official said on condition of anonymity, adding they fled the scene after the shooting.
The victim was shot dead in his car in the neighbourhood of Sena, he added.
The US embassy in Sanaa said it did not have information about the killing and was investigating.
The attack comes two days after an official said suspected Al-Qaeda gunmen abducted a Swiss woman, also a teacher at a language school, in the Red Sea port of Hodeida and moved her to the restive Shabwa province further east.
Al-Qaeda local branch is active in the south and east of Yemen, but not in Taez, which was a major centre for the year-long opposition movement against former President Ali Abdullah Saleh, that forced the veteran leader to step down last month.
More than 200 people have been abducted in Yemen during the past 15 years, many of them by members of the country's powerful tribes who use them as bargaining chips with the authorities.
Almost all of those kidnapped were later freed unharmed.