At least three people were killed and seven others injured in a blast in Quetta on Wednesday, police and witnesses said. According to police, the blast took place near Balochistan University in Shafi Colony on Sariab Road when some miscreants threw a grenade at a police van. Witnesses said unidentified persons threw a hand grenade at the police van when it was on routine patrol. Another police van escaped the attack. The police van was completely destroyed, witnesses said, adding one police was killed. The injured included four policemen and some passers-by, a private TV reported. The injured were shifted to the local hospital and doctors said several injured are in critical condition. Police cordoned off the area and bomb disposal squad also reached the site. The attackers fled after the incident and police launched a search operation in the city to arrest the suspects. No group has claimed responsibility for the attack. The authorities suspect anti-government nationalist groups were behind such attacks, who are demanding more political rights and share in the natural resources in the province.