The attackers from the Ansar al-Sharia group, which is on the US terror list, opened fire at 20-year-old Hashem al-Asmi late Monday in the provincial capital of Huj, the source told AFP, adding that the gunmen fled on their motorbike after killing Asmi.

Ansar al-Sharia is the local branch of Al-Qaeda in Yemen where the network, although weakened, is still active mainly in the southern and eastern parts of the country.

Al-Qaeda loyalists seized large swathes of Yemen's south and east in 2011, taking advantage of a decline in central government control during an 11-month uprising that forced veteran president Ali Abdullah Saleh from power.

Yemeni government troops have since recaptured much of the territory with support from US drone strikes, but the jihadists retain bases in the desert east and frequently carry out hit-and-run attacks using unlicensed motorbikes.

During their control of these areas, the militants had tried to impose a strict version of sharia (Islamic law) on residents, executing or lashing citizens they accused of various crimes. They had also severed the hands of many accused of burglary.