A victim is seen at the scene of a suicide car bomb attack in Kabul, Afghanistan on Jan. 16. (Ahmad Jamshid/AP)

Six attackers launched a deadly assault on the headquarters of Afghanistan’s intelligence agency Wednesday, according to Afghan officials. At least one agency employee was killed, and more than 30 civilians were injured.

At least one assailant detonated a car bomb at an entrance of the National Directorate of Security’s walled compound in central Kabul on Wednesday afternoon, while five others attempted to shoot their way inside, according to the city’s police chief, Lt. Gen. Mohammad Ayub Salangi.

In a statement, the security agency said the bomb was made of a “new type of explosive material” and was gel-based.

The Taliban asserted responsibility for the attack. All six assailants were killed by Afghan security personnel.

Initial reports said two employees of the agency died in the attack, but officials later revised that figure to one.

Despite the relatively small toll, the attack added to questions about insurgents’ ability to penetrate deep into what is known as the “Kabul security zone.” The intelligence headquarters is in a neighborhood of shops and offices, dozens of which were damaged in the assault.

As the U.S. military drawdown continues, the American strategy is increasingly focused on securing the Afghan capital, where about a third of the country’s population lives.

The security agency has been a common target for insurgents in recent months. Its director, Asadullah Khalid, was badly wounded last month in an assassination attempt in an agency guesthouse. Attacks in October killed intelligence agents in the southern provinces of Kandahar and Helmand.

In a statement, the Taliban said Wednesday’s attack occurred before the end of an important meeting at which several foreign advisers were present. The bomb went off when “key enemy individuals started to come out of the compound,” the group said.

Officials for the NATO-led International Security Assistance Force denied the assertion.

“There were no ISAF personnel affected in any way,” said Lt. Col. Les Carroll, a spokesman for the coalition.