An armed man riding a motorcycle assassinated an officer of the Political Security on Thursday in the heart of the capital Sana'a, security sources said.
Security sources said the officers is Yahya Badi, 45 years old, and there was no immediate claim of responsibility.
Yemen's defense ministry claimed that the attacker is a member of al-Qaeda, pointing out that he could escape.
The shooting came the same day a security official said a U.S. drone attack killed at least four suspected Islamist militants in a car in a remote province of eastern Yemen.
Assassinations of top intelligence officers have increased since last year, with outlaws obviously taking advantage of the unrest roiling the country.
A number of Yemeni intelligence officers of the political security were killed in Sana'a, Baidha, Aden, Taiz and Hadhramout and other governorates.
Lt. Col. Mohammed al-Qudami, who was the intelligence chief for one of the sectors of Sana'a, was killed early of July.
In the mid of August, armed men attacked the Political Security's building in Aden, killing about 20 soldiers and wounding dozens more.
After the Yemeni government announced its victory in early June, the al-Qaida carried out a suicide bombing various governorates and killed the commander of Yemen's southern military region, Salem Qatan.

It also launched a suicide attack in the capital Sana'a on July 11 that killed more than 20 police cadets.
The Yemeni capital, Sana'a, and other major cities have witnessed a state of loose security as crimes of killing and weapon carrying increased after a year of pro-democracy protests that swept the country.