How the bomber managed to pass through layers of Raziq's security is the focus of investigation now [EPA]

The police chief of Afghanistan’s southern Kandahar province has survived an assassination attempt after a teenage bomber managed to slip through tight security into the police headquarters.

Authorities said officers spotted the bomber and opened fire before he could reach Brigadier-General Abdul Raziq, 32, although he managed to detonate his explosives during Wednesday's attack in Kandahar city.

One policeman was wounded in the attack, which came less than a year after a suicide bomber killed the previous Kandahar police chief, Khan Mohammad Mujahid, in his compound. The Taliban claimed responsibility for the killing.

Wednesday's assault raises concerns about security in an area that was the birthplace of the Taliban and has been a focus of efforts by a surge of US troops to boost Afghan government control in the south.

"The 15-year-old boy had a letter for me and wanted to meet me," Raziq said.

"But as soon as he got near my office, a policeman noticed he [had explosives] and started to shoot him."

Raziq said the attacker detonated his explosives on the spot.

An investigation has been launched to find out how teenager managed to pass several layers of security with explosives strapped on his body.

Raziq, who also commands the border police in southern Afghanistan, is considered one of the most powerful men in the south after the assassination of Ahmad Wali Karzai, brother of Afghan President Hamid Karzai and a major power broker in the area.

Despite the presence of more than 100,000 foreign troops, violence across Afghanistan remains at its worst levels since the Taliban was toppled by US-backed Afghan forces in late 2001, according to the UN.

On Tuesday, three suicide bombers stormed a government building in eastern Paktika province, killing four government employees and three policemen. The Taliban claimed responsibility for the attack.

Foreign forces are in the process of handing control of security over to the Afghan army and police in the run-up to the 2014 withdrawal date.