At least four was killed and about a dozen others were injured Sunday when a suicide bomber riding on a bicycle hit a police van in Quetta.

A police van damaged in a blast is seen in Quetta, capital of southwestern Pakistani province of Balochistan, March 21, 2010. At least four people were killed and about a dozen others were injured on Sunday when a suicide bombing hit a police van in Quetta. (Xinhua/Iqbal Quetta)

Chief of Pakhtoonkhawa Milli Awami Party, Mehmood Khan Achakzau, was not at home when the bomb ripped through the busy area, his family said.

The injured, including several policemen, were taken to Civil Hospital. Doctors said five injured are registered as critical.

No group claimed responsibility for the attack.

Quetta has seen wave of targeted killings in recent days, police said.

On Saturday, gunmen shot dead at least four people belonging to ethnic Harzara Shiite community in Quetta.

VietNamNet/Xinhuanet