At least six persons were killed and and 200 injured when police moved in to disperse the demonstration earlier Saturday, sparking fierce clashes.
The operation was launched after Islamabad High Court (IHC) on Friday issued contempt of court notice against Interior Minister Ahsan Iqbal for failing to implement orders to clear the roads.
Smoke and tear gas filled the air as the roughly 8,500 elite police and paramilitary troops in riot gear were also seen throwing rocks and using slingshots in the ongoing bid to clear 2,000 or so hardline demonstrators which began soon after dawn.
The Pakistani government has called on the powerful military to deploy in the capital Islamabad. The request was made by Islamabad Capital Territory authorities, according to an interior ministry order, which said the federal government had authorised the deployment of "sufficient troops" to "control law and order" in the city until further notice.
According to the Express Tribune, following the PEMRA order, there has been a media blackout in Islamabad, where almost all leading private TV channels have gone off-air.
About 2,000 activists of Tehreek-i-Khatm-i-Nabuwwat, Tehreek-i-Labaik Ya Rasool Allah (TLYR) and the Sunni Tehreek Pakistan (ST) for more than two weeks have been blocking the Islamabad Expressway and Murree Road that connect Islamabad with its only airport and the garrison city of Rawalpindi.
The protesters demand the resignation of law minister Zahid Hamid for changes made about Khatm-i-Nabuwwat or finality of prophethood oath in the Elections Act 2017 passed in September.
Islamabad city magistrate on Friday issued a warning to protesters to disperse by midnight or face the consequences.
TV footage showed police firing tear gas and security personnel in riot gears charging at the protesters.
Dozens of them were arrested and shifted to various police stations. Some of the security personnel were injured due to stone pelting by protesters.
The operation was still going on and police were facing stiff resistance from the protesters.
Earlier, IHC last Friday had given a 24-hour deadline to the government to clear the roads, which was later extended until Thursday.
However, the court on Friday expressed strong displeasure at the government for failing to take action against the protesters.
OneIndia News (with agency inputs)