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Rahmat Gul, Associated Press
Afghan police gather at the site of a suicide attack in Kabul, Afghanistan, Sunday, Nov. 9, 2014. A bomb exploded on Sunday morning at the police headquarters in Afghanistan's capital Kabul, killing at least one officer and wounding several others, officials said.

KABUL, Afghanistan — Afghan authorities are investigating how a suicide bomber was able to strike deep inside the heavily guarded police headquarters in central Kabul on Sunday in an apparent attempt to assassinate the city's chief of police.

The Taliban bomber's ability to pass through heavy security and make his way to within meters of Gen. Mohammad Zahir Zahir's office has revived concerns that insurgents have penetrated Afghanistan's security and intelligence forces.

The attack, which killed a senior police officer and wounded at least seven people, also highlighted the vulnerability of Kabul to a determined and still-virulent Taliban insurgency as a dwindling number of U.S. and NATO troops shift from a combat role to training and support by the end of this year.

"The man was wearing a civilian suit and had a file in his hand and the suicide vest under his clothes," Interior Ministry spokesman Sediq Sediqqi said.

"He was asking police directions to the chief of police's office, saying he had papers to deliver to him. This is the procedure for anyone who wants to meet with the chief of police, so the police sent him in the right direction."

Earlier, Zahir said that the man was wearing a military uniform. Sediqqi said that footage from closed-circuit television clearly showed the attacker's route through the compound.

Zahir was not in his office on the third floor of the building at the time of the attack, around 9 a.m. (0430 GMT), but he was in the compound, Sediqqi said. "He was definitely the target," he said.

NATO's International Security Assistance Force said that none of its personnel were injured in the attack, and there were no reports that anyone attached to ISAF was at the site at the time.

Zahir's chief of staff, Col. Mohammad Yasin, was killed in the attack, according to police and the health ministry. Health Ministry spokesman Kaneshka Baktash Turkistani said a small child was among the wounded.

The compound is in one of the most heavily guarded areas of Kabul and also houses the office of the Kabul provincial governor, the Appeals Court and police detention centers for men and women.

It is surrounded by high concrete blast walls, with turrets manned by paramilitary police armed with Russian-made PK heavy machine guns. Visitors must past through a number of checkpoints, including body searches and x-rays, before reaching the main buildings.

Abdul Jabar Taqwa, the Kabul provincial governor, said windows across the compound were shattered by the blast. "I was in my office in the building opposite the Kabul police chief's building when the explosion happened. It was a strong blast and shattered all the windows in my office," he said.

Insurgents have intensified attacks on the Afghan capital in the past year, coinciding with a drawn-out presidential election and the inauguration in September of President Ashraf Ghani.

The explosion came about two hours after another blast was heard in the city. Defense Ministry spokesman Gen. Mohammad Zahair Azimi said that explosion was an attack on an Afghan army vehicle that resulted in no casualties.

Taliban insurgents claimed responsibility for both attacks.

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