Yemeni security officials say a gunman has assassinated the Yemeni chief of security at the U.S. Embassy in Sanaa.

The officials say Qassem Aqlani, who was in his fifties, was shot dead while on his way to work early on Thursday. They say a gunman on a motorcycle opened fire at him and fled the scene.

Aqlani had been working for the U.S. Embassy in the Yemeni capital for nearly 20 years.

The Yemeni officials spoke on condition of anonymity because they were not authorized to speak to the media.

The attack comes as Yemen's U.S.-backed government is waging an offensive against al-Qaida's branch in the country, taking back territory and cities in the south that the terror group seized last year.