KABUL, May 12 (Xinhua) -- At least one police officer was wounded after an explosion ripped through a busy road in the western part of Kabul, the capital of Afghanistan, on Sunday, witnesses said.

"A bombing struck a police vehicle in Dar-ul-Aman road in Police District 6 at 4:15 p.m. local time. The vehicle caught fire after the blast, sending a thick black smoke above the area," witness Mustafa Qurrishi told Xinhua.

The area was cordoned off by police and the wounded was shifted to Istiqlal Hospital on the road, he said.

Basir Mujahid, Kabul's police spokesman, told Xinhua that the vehicle was belonged to Criminal Investigation Department of Kabul police and the blast was caused by a sticky bomb attached to the running van.

The capital city with a population of nearly 5 million has been hit by series of terror attacks over the past couple of years.

On Wednesday, nine people, including five police officers, were killed and 20 people wounded in a Taliban attack and a deadly suicide car bomb blast against a U.S.-funded aid agency in central Kabul.