The Shehbaz Sharif governmen in the early hours of Thursday called in the army to protect the Red Zone of Islamabad as Imran Khan's Azadi March entered the capital city of Pakistan.
The army was deployed to protect the government buildings and the Pakistan secretariat.
The Pakistan Supreme Court on Wednesday permitted Imran Khan's party to hold his Azadi march in Islamabad and restrained the government from arresting Pakistan Tehreek-e-Insaf workers.
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Clashes between PTI workers and the police was also reported in Punjab, Lahore and Karachi, before the march entered the capital.
PTI claimed that the police opened fire on people who had gathered in support of the Azadi march in Lahore.
Just as Imran Khan reached Islamabad, continuous tear gas shelling was reported in the city.
Pakistan's ex-Prime Minister Imran Khan has demanding holding of fresh polls by the Shehbaz Sharif government. Khan warned the government that if the dates for elections are not announced within six days, he will again come to Islamabad.