ISLAMABAD, July 16 (Xinhua) -- At least three people were killed and 11 others injured when unknown militants fired a rocket-propelled grenade at a passenger bus in Pakistan's southwestern Balochistan province on Wednesday, local rescue and police officials told Xinhua.

The incident happened in Kalat district when the bus was traveling from the country's southern port city of Karachi to Balochistan's capital city Quetta, said Muhammad Zeeshan, manager of operations of the rescue department at non-governmental organization Edhi Foundation in Quetta.

Talking to Xinhua, police sources from the district said that the attack happened at around 5:20 p.m. (12:20 GMT) local time when attackers fired a rocket-propelled grenade at the bus, killing the three passengers on the spot and injuring 11 others.

Rescue teams shifted the injured to the District Headquarters Hospital in Kalat, where several remain in critical condition, Zeeshan said.

Following the incident, security forces cordoned off the area and launched a search operation to trace the attackers.

No group has claimed responsibility for the attack yet.

Balochistan has witnessed a surge in militant attacks in recent months, with frequent incidents targeting civilians, security forces, and public transport on major highways. ■