Tens of thousands of people have taken to the streets in Pakistan's capital Islamabad to demand the resignation of Prime Minister Imran Khan.

An Islamist political party and other opposition forces called for the protest on Friday, denouncing last year's parliamentary election as rigged.

People called for Khan and his administration to step down, and for parliament to be dissolved.

The leader of the protests said the prime minister will face stronger protests that would be difficult to quell, unless he resigns within two days.

The government has deployed police officers and security forces across the city in an attempt to stop the rallies expanding.