Suspected Taliban militants killed a district chief and three of his staff in an ambush in eastern Afghanistan on Thursday, while in the south rebels killed a police commander and his brother, officials said.

Separately, a suicide car bomber killed himself and wounded six Afghans in a botched attack on a U.S.-led coalition convoy in Kandahar city, the former Taliban stronghold in the country's south, police said.

Thursday's violence followed a rare attack a day earlier on a coalition military base in Helmand's Sangin district, which killed an American and a Canadian soldier and sparked fierce U.S.-led retaliation that left 32 insurgents dead in the bloodiest fighting in months.

Dawlat Shah district chief Qadeer Khan and three of his staff were killed by Taliban militants firing rockets and rifles at their car as Khan drove home, said Habib Rasool Memawal, deputy governor in the eastern Laghman province.

The police commander of Musa Qala, a district in the southern Helmand province, and his brother were killed when their vehicle was attacked on the road between Musa Qala and the nearby town of Toughi, said Mullah Amir Akhandzada, Helmand's deputy governor.

"Taliban attacks have been increasing recently in Helmand province, but we have taken measures to prevent such attacks by deploying Afghan army and police forces in all areas and the coalition is helping a lot," Akhandzada told The Associated Press Thursday.

Taliban militants have warned that they would be stepping up attacks against Afghan and coalition forces during the spring season.

The police chief's bodyguards exchanged gunfire briefly with the militants before they fled the scene, said Akhandzada. It was unclear if any insurgents were wounded.

Akhandzada said the slain commander, who was identified only by his first name of Pacha, was a well-known jihadi leader who fought Russian forces during the Soviet occupation of Afghanistan.

In the neighboring southern Afghan province of Kandahar, a suicide attacker detonated his car bomb near a foreign military convoy on Thursday, killing himself and wounding six Afghan passers-by, police and witnesses said.

One of the victims, Mohammed Ibrahim, said he saw a car blow up near the vehicles, none of which were damaged. The troops were not injured.

The attack is the latest in a string of suicide bombings to hit southern Afghanistan in the past six months, representing a new and disturbing trend four years after the ouster of the hardline Taliban regime.