Updated at 5:56 a.m. Eastern
KABUL, Afghanistan Six militants one driving a car packed with explosives attacked the gate of the Afghan intelligence service in the capital Kabul on Wednesday, setting off a blast that could be heard throughout downtown and which sent a plume of dark smoke rising into the sky.
Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack in a text message sent CBS News and other media organizations.
Sidiq Sidiqi, a spokesman for the Interior Ministry, told CBS News Kabul bureau chief Mukhtar Ahmad that 30 civilians were injured in the attack. An NDS source said 4 of the agency's guards were killed, but the intelligence agency would not immediately confirm the deaths.
The explosion occurred about noon local time and was followed by volleys of gunfire for the next 45 minutes. As the car bomber drove into the gate, the five others attacked on foot, said Mohammad Zahir, the chief of the Kabul police investigation unit. All the assailants were killed in the fighting, he said. It was not immediately clear if some of the men on foot were also were wearing suicide vests.
An Associated Press reporter at the scene saw at least 10 wounded people being taken away in ambulances. The windows of nearby shops were blown out and reporters could see the mangled wrecks of at least seven cars that had been caught up in the explosion. The NDS compound is surrounded by tall, thick cement walls designed to protect buildings from bomb blasts.
An eyewitness who was wounded by flying glass, Mohammad Zia, said he saw a car drive up to the NDS gate and blow up. It was the second attack aimed at the intelligence agency in two months. On Dec. 6, a Taliban suicide bomber posing as a messenger of peace blew himself up while meeting with agency chief Asadullah Khalid inside a Kabul residence he used to receive guests.
The attack seriously wounded Khalid and he has since then been hospitalized at a hospital in the United States.
Speaking to CBS News' Sami Yousafzai by phone after Wednesday's attack, the Taliban commander for military operations inside Kabul, Qari Talha, said the operation was meant as a message to Khalid.
"If he comes back, we will not spare him this time," said Talha, adding that the attack was also planned to show, "those who think and make comments that the Taliban is weaker; we are still strong and will speed up our attacks inside Kabul and other cities."
Talha said there were Taliban militants behing held as prisoners inside the NDS headquarters, and he vowed they would soon be free.
Attacks in the heavily secured Afghan capital are less common than in the restive south, but they do occur and are often sophisticated strikes with multiple attackers that aim to penetrate past the perimeters of armed guards and blast walls that surround government buildings and embassies.
The most recent attack in Kabul was on Dec. 17, when a car bomber struck outside a compound used by a U.S. military contractor. That blast killed at least two Afghan workers and wounded more than a dozen other people.
A spokesman for the international military coalition in Afghanistan confirmed an explosion and small arms fire but did not provide further details. Maj. Martyn Crighton said that Afghan forces were responding to the attack and there was no involvement from the NATO military coalition.