LAHORE, Pakistan (AP) — Pakistani authorities have opened a murder investigation against an anti-government cleric after a police officer was killed in clashes with the cleric’s supporters, a top Pakistani official said Sunday.

The clashes and murder investigation are part of escalating tensions in Pakistan where two high-profile figures — the cleric and cricket legend-turned-politician Imran Khan — have called for the government’s ouster. Both are calling for a march on the capital Islamabad on Thursday, vowing to bring thousands of people into the streets and throw the government into crisis.