Unidentified gunmen opened fire on a police vehicle on Thursday, killing three police officers in Pakistan's biggest city Karachi.<br/> <br />Authorities said a police vehicle was on routine patrol in the centre of the city when it came under fire.<br/> <br />The policemen were rushed to a nearby hospital, where they died.<br/> <br />The motive behind the killings was unclear, and police said they're investigating the attack.<br/> <br />Karachi has a long history of violence, and ethnic, religious and sectarian disputes can often explode into battles engulfing entire neighbourhoods.<br/> <br />More than two dozen people have been killed in the city over the past week alone.<br/> <br />Travis Brecher, Reuters
