A masked gunman assassinated a Yemeni security official who worked for the U.S. Embassy in a drive-by shooting Thursday near his home in the capital, officials said, adding the assault bore the hallmarks of al-Qaeda's Yemen branch.

The attack comes amid a sharp deterioration of security in Yemen and several other Muslim countries since the collapse of police states controlled by autocratic leaders during a wave of uprisings known as the Arab Spring.

An elite team of some 50 Marines that was sent to Sanaa to bolster security at the U.S. Embassy after a Sept. 13 attack by protesters was scheduled to leave later Thursday and it was not clear if the attack would affect those plans, Yemeni officials said.

The officials noted it was similar to a series of other recent assaults by Al-Qaida's Yemen branch, although they said it was too early to confirm the group's involvement. Washington considers the Yemen-based Al-Qaida in the Arabian Peninsula, or AQAP, the most dangerous offshoot of the terror network. It has also been increasingly targeting Yemeni intelligence, military and security officials in retaliation for a U.S.-backed government offensive in the south.

Slain official worked at embassy for nearly 20 years

Yemeni security officials, who spoke on condition of anonymity because they weren't authorized to release the information, identified the slain embassy security official as Qassem Aqlani, in his 50s.

He was on his way to work when a gunman on a motorcycle opened fire at him and fled the scene, they said. The attack was near Aqlani's home in western Sanaa, while the embassy is located in the eastern half of the city.

Aqlani had been working for the U.S. Embassy for nearly 20 years, most recently as a lead investigator into last month's assault on the compound by Yemenis protesting the film that mocked the Prophet Muhammad, the officials said. Protesters stormed the embassy and set fire to a U.S. flag before government forces dispersed them with tear gas.

Al-Qaeda's Yemen branch has called for attacks on U.S. embassies in a bid to take advantage of the anti-American sentiment that has swept the Middle East and other parts of the Muslim world in the past month over the film.

Initially, the film was linked to a Sept. 11 attack on the U.S. Consulate in the Libyan city of Benghazi that left four Americans dead, including U.S. Ambassador Chris Stevens. U.S. officials said later the attack was not linked to the video.

AQAP praised the killing of U.S. diplomats in Libya, describing it as "the best example" for those attacking embassies to follow.

Political vacuum after Arab Spring

The group had taken advantage of a security and political vacuum created by last year's uprising that led to the ouster of longtime leader Ali Abdullah Saleh and seized territories and cities in the south. The government-led offensive has pushed the militants out to mountainous areas from where they have been staging suicide attacks and assassinations inside cities.

Two weeks ago, a top intelligence official, Col. Abdullah al-Ashwal, was also killed in a drive-by shooting in Sanaa.

The U.S. Embassy in Sanaa, located in an upscale eastern neighbourhood called Dhaher Hameer, has been heavily fortified with new protective measures amid the turmoil surrounding the uprising, and security was tightened even more after the latest assault on the embassy by protesters on Sept. 13.