Two gunmen on a motorcycle killed an employee of the US Embassy in Sana'a, Qasim Aqlan, on Thursday, sources of Yemen's Interior Ministry affirmed.

Yemeni sources said that Aqlan worked as an investigation officer of the embassy and he was tasked to probe into the storm against the embassy on September 13, 2012.

The sources affirmed that masked gunmen shot fire on Aqlan's car, leaving him killed, pointing out that the incident occurred in al-Siteen street, close to the residency of Yemen's president Abdu Rabo Mansour Hadi.

Angry protesters stormed the US Embassy in Sana'a early of September in protest against the US-made offensive film on Prophet Mohammad. About three protesters were killed and 30 more were inured.

Yemeni observers had said that Yemen's security forces allowed the protesters to easily exceed the security barrier and enter the embassy gates.

Yemeni militant groups such as al-Qaeda and the Houthi group exploited the US-made anit-Islam film to incite against the United States.

A Yemeni think-tank, Abaad Research and Study Centre has recently said that slogans raised by the Houthi group led to the storm of the US Embassy in Sana'a early of September.

The main slogan of the Houthi group is "God is Great, Death to America, Death to Israel, a curse on the Jew."

The Houthi group that has recently allied with the former president Ali Abdullah Saleh and his family started to spread and print its slogans on most streets of Sana'a, Yemeni analysts say.