A Yemeni security official says gunmen have shot dead a senior intelligence officer as he was riding in his car in a southern city.

The official says Col. Marawan al-Moqbouli was assassinated on Thursday in Aden. The official spoke on condition of anonymity because he was not authorized to speak to media.

Yemen has witnessed a string of suicide bombings, assassinations and drive-by shootings by suspected militants affiliated to al-Qaida in the Arabian Peninsula. The Yemen offshoot is considered by Washington as group's most dangerous branch.

Tensions with regionalists have also been on the rise in the south, formerly an independent country.