The police in the city of Rawalpindi on Friday used tear gas in clashes with stone-throwing supporters of Pakistani opposition leader Imran Khan defying a ban on public gatherings.
There was no immediate report of injuries but TV stations carried footage of police firing tear gas and charging with batons at rock-hurling protesters.
Several key roads in Rawalpindi, about 20 km (12 miles) from Islamabad, have been blocked off with containers ahead of Khan´s planned appearance at a political rally.
On Thursday, the officials banned all public rallies in Islamabad and Rawalpindi.