KABUL, Afghanistan — A suicide bomber targeted a police convoy in Afghanistan's southern Helmand province on Monday, killing two people, a policeman and a civilian, a local official said.

The attack took place in the Helmand provincial capital of Lashkar Gah, said Omar Zwak, the spokesman for the provincial governor. He said the explosion also wounded 15 people — eight policemen and seven civilians. The police convoy was en route to the district of Sangin for an operation there, he added.

No group claimed responsibility for the attack, but the Taliban frequently use roadside bombs and suicide attacks against Afghan and NATO forces and government offices in the country.

Helmand is one of the most dangerous and insecure of the country's provinces. Last month, hundreds of Taliban insurgents attacked several Afghan security checkpoints in Sangin district. After a week of intensive battles, more than 100 people were killed and dozens were displaced from their homes. The government subsequently deployed nearly 2,000 reinforcements there.

Insurgents also targeted Afghan security forces in overnight attacks.

In northern Afghanistan, Taliban fighters ambushed a local police checkpoint in the Qaysar district of Faryab province, an official said.

At least eight local policemen and 27 Taliban fighters were killed in the firefight that ensued, according to the provincial governor, Mohamadullha Batash.

In southern Uruzgan province, four Afghan policemen were shot to death at a checkpoint in Shahid Asass district, said Dost Mohammad Nayuib, spokesman for the Uruzgan governor.

The attackers were two other policemen from the same unit who fled the scene, said Nayuib. Another policeman was wounded in the attack, he added.

It was not immediately clear what motivated the attack, which could be the latest incident of insider attacks in which Afghan security turn on their colleagues or NATO partners.

"An investigation is underway to find the reason behind this attack," Nayuib said.

The attacks and the fighting are shaping up as a major test of the Afghan government's ability to maintain security in volatile areas after foreign combat troops leave by the end of 2014.