Officials say a stampede at an anti-government rally in central Pakistan killed seven supporters of famous cricketer-turned-politician Imran Khan.

Government official Zahid Saleem says the incident took place late on Friday at a stadium in the city of Multan.

The stampede happened at the end of the rally, when Khan's supporters tried to push their way out of a gate after listening to his speech at a local stadium. Forty people were also injured.

Police said over 40,000 people attended the rally. The seven killed were crushed to death during the stampede.

Khan has led mass sit-ins in the capital, Islamabad, since August, demanding Prime Minister Nawaz Sharif step down over alleged fraud in the 2013 elections.

Pro-Khan rallies elsewhere in Pakistan have been mostly free of violence.