Islamabad, March 21 (IANS) At least four people were killed and a dozen injured Sunday when a suicide bomber riding on a bicycle hit a police van in Quetta, capital of Pakistan's southwestern Balochistan province.

Five injured policemen were in critical condition, Xinhua reported.

The bomb exploded near the residence of a senior political leader, Mehmood Khan Achakzau, who heads the Pakhtoonkhawa Milli Awami Party.

He was not at home when the bomb ripped through the busy area, his family said.

The injured, including several policemen, were taken to hospital. Doctors said five of them were in a critical condition.

Quetta has witnessed wave of targeted killings in recent days. On Saturday, gunmen shot dead four people belonging to ethnic Harzara Shia community in Quetta.