ISLAMABAD, July 19 (Xinhua) -- At least four people were killed in a Pakistani city Saturday as police opened fire at demonstrators, who were protesting against an earlier incident of firing, witnesses and police said.

    Two policemen were among 12 people injured in the clash in Quetta, the capital city of southwestern Balochistan province.

    Local media quoted police as saying that they returned fire when some demonstrators fired at them on the Baruri road.

    Angry people were protesting against an earlier incident in which unidentified people opened fire at a car, killing one person and injuring another.

    They were chanting slogans against the government's failure to check violence in Quetta and other parts of the province.

    When the police were approaching the venue of the demonstration, someone from the rally fired at them and they returned fire.

    The hospital sources confirmed two people dead and 12 others injured including a police inspector and another police constable. TV channels said that four people died in the clash.

    The demonstrators then took positions in the nearby mountains and fired at the police, witnesses and TV channels said.

    The police then called more forces to check the violence, reports said.