Mohammad Zahir Zahir, Kabul police chief, survives assassination attempt

Afghan authorities are investigating how a man wearing an explosives-packed vest was able to infiltrate the heavily guarded police headquarters in central Kabul on Sunday and attempt to assassinate the city's chief of police.

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

The incident was a serious breach of security in the fortified centre of the capital and has 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.

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Sediq Sediqqi, spokesman for the interior ministry, said the incident had raised questions about someone "wearing a suicide vest had breached security".

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

"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 the man was wearing a military uniform. Sediqqi said 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, Sediqqi said, "but he was definitely the target."

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

1 killed, 7 wounded

Zahir's chief of staff, Col. Mohammad Yasin was killed in the attack. At least seven others were wounded, according to police and the health ministry. Kaneshka Baktash Turkistani, spokesman for the health ministry, said the wounded included a small child.

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 centre 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 at the police headquarters. "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. Defence 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.