Four border policemen were killed by a roadside bomb in southern Afghanistan on Friday.

Four border policemen were killed by a roadside bomb in southern Afghanistan which also left two others wounded, officials said Friday.
The incident happened in Kandahar province's Spin Boldak district, close to the border with Pakistan, late Thursday. The Taliban claimed responsibility in a text message to AFP.

"Four border policemen were killed and two were injured when a roadside mine blew up their vehicle in Spin Boldak district yesterday evening," General Abdul Raziq, the regional chief of Afghanistan's border police, told AFP.

The attack is the latest in a wave of strikes against Afghanistan's police and army in the run-up to the start of the transition from foreign to Afghan security control in July.

Last Friday, the police chief of Kandahar, seen as the Taliban's heartland, was assassinated. A day later, nine troops including five foreigners were killed by a suicide bomber at an Afghan army base in the east.

On Monday, three people died when a would-be suicide bomber in a soldier's uniform got inside the defence ministry in Kabul, one of the country's worst security breaches in years.

Elsewhere in Afghanistan, police said that three security workers for a construction company had been killed by a NATO air strike late Thursday in the eastern border province of Khost.

The NATO-led International Security Assistance Force (ISAF) said it was still looking into what happened.

Khost police chief Abdul Hakim Ishaqzai told AFP: "Our reports say that the individuals in Speyreh district were firing their weapons for fun and an ISAF attack helicopter spotted them.

"The helicopters mistook them for insurgents and attacked them, killing three and wounding one."

ISAF spokesman Major Michael Johnson said its reports "suggest that three or four individuals fired on one of our helicopters" and that the helicopter "returned fire killing them."

"But we are continuing to look into the information to figure out exactly what occurred.”

Meanwhile, 14 insurgents were killed overnight in military operations in the southeastern province of Paktika, the governor's office said.

International combat troops in Afghanistan are due to leave the country completely in 2014, when Afghan forces are scheduled to take responsibility for their own security.