An Afghan official says a suicide bomber detonated his vehicle as it was being followed by police on the outskirts of the capital Kabul, killing a police officer and wounding three others.

Hashmat Stanekzai, spokesman for the Kabul provincial police chief, says the police were following the attacker's vehicle Thursday morning, as they suspected he was trying to enter the city.

"A suicide bomber was trying to enter Kabul with the intention of detonating explosives in a crowded part of the city," Stanekzai said. "He was being followed by police."

The Taliban claimed responsibility. The insurgents have stepped up attacks in recent months, concentrating on government, military and foreign targets in major cities.

The U.S.-led international combat mission ends on Dec. 31.