Pakistani police fired tear gas at stone-throwing supporters of opposition leader Imran Khan, who defied a ban on public gatherings, adding to political deadlock ahead of his plans to shut down the capital next week.

There was no immediate report of injuries but local TV stations carried footage of police charging with batons on Friday, as plumes of tear gas billowed in the air.

Several key roads in Rawalpindi, about 20km from the capital Islamabad, have been blocked off with containers ahead of Khan's planned appearance at a political rally.

Police surrounded the home of former cricketer Khan, who called for nationwide protests after dozens of activists from his Pakistan Tehreek-e-Insaf (PTI) party were arrested a day earlier. 

The protests have added to the chaos ahead of Khan's plans to lock down the capital next Wednesday in what he described as a final push to force Prime Minister Nawaz Sharif to resign over corruption allegations.

Khan had vowed to join Friday's planned rally but had not left his home, with a heavy police presence outside, by the afternoon and was scheduled to hold a press briefing. 

The rising tensions come at an awkward time for Sharif, with relations between his ruling PML-N party and the powerful military strained over a newspaper leak about a security meeting that angered army officials.

Police said the rally contravened a city order issued hours earlier to ban all public gatherings in the capital ahead of next week's protests. 

On Thursday evening, authorities swooped on an indoor youth rally by Khan's party in Islamabad, beating activists with batons and detaining 38 people.

PTI leaders were infuriated by the police raid, further fraying relations ahead of the planned protest.

"The government has proved that there is no democracy in Pakistan. It is a monarchy," PTI politician Asad Umar told reporters from the scene.

Khan, who led a weeks-long occupation that paralysed the government quarter of Islamabad two years ago after rejecting Sharif's decisive election win, has vowed to contest orders banning public gatherings in court but has hinted his supporters would march on the capital next week regardless.

PTI chief Imran Khan was due to attend the Islamabad rally [EPA/Bilawal Arbab]

A top administrative official in Rawalpindi has also banned protests in the city.

Islamabad Deputy Commissioner Ahmed said PTI would need permission in the form of an NOC if it plans to host any events, including Wednesday's shutdown strike.

At the centre of Khan's latest challenge to Sharif's government are leaked documents from the Panama-based Mossack Fonseca law firm that appear to show that Sharif's daughter and two sons owned offshore holding companies registered in the British Virgin Islands. Sharif's family denies wrongdoing.

Holding offshore companies is not illegal in Pakistan, but Khan has implied the money was gained by corruption.

The ruling party has dismissed Khan's plans to shut down Islamabad as a desperate move by a politician whose popularity is waning ahead of the next general election, likely to be held in May 2018.

"Pakistan is going towards becoming a developed country, and the opposition is worried that if this system of development continues until 2018, then by then their politics will be finished," said Sharif at a gathering of party workers on Friday. 

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Source: News Agencies