ISLAMABAD (AP) — Pakistani security forces launched an operation Tuesday night to disperse supporters of imprisoned former Prime Minister Imran Khan who had gathered in the capital to demand his release from prison.

The latest development came hours after thousands of Khan supporters, defying government warnings, broke through a barrier of shipping containers blocking off Islamabad and entered a high-security zone, where they clashed with security forces, facing tear gas shelling, mass detentions and gunfire.

Tension has been high in Islamabad since Sunday when supporters of the former prime minister began a “long march” from the restive northwest to demand his release. Khan has been in a prison for over a year and faces more than 150 criminal cases that his party says are politically motivated.

Khan’s wife, Bushra Bibi, led the protest, but she fled as police pushed back against demonstrators. Hundreds of Khan’s supporters are being arrested in the ongoing nighttime operation, and police are also seeking to arrest Bibi.

Interior Minister Mohsin Naqvi told reporters that the Red Zone, which houses government buildings and embassies, and the surrounding areas have been cleared. Leaders from Khan's Pakistan Tehreek-e-Insaf party, or PTI, have also fled the protest site.

Earlier Tuesday, Pakistan’s army took control of D-Chowk, a large square in the Red Zone, where visiting Belarusian President Alexander Lukashenko is staying.

Since Monday, Naqvi had threatened that security forces would use live fire if protesters fired weapons at them. “We have now authorized the police to respond as necessary,” Naqvi said Tuesday while visiting the square.

Before the operation began, protester Shahzor Ali said people had taken to the streets because Khan had called for them. “We will stay here until Khan joins us. He will decide what to do next,” Ali said.

“If they fire bullets again, we will respond with bullets,” he said.

Protester Fareeda Bibi, who is not related to Khan’s wife, said people have suffered greatly for the last two years.

“We have really suffered for the last two years, whether it is economically, politically or socially. We have been ruined. I have not seen such a Pakistan in my life,” she said.

Authorities have struggled to contain the protest-related violence. Six people, including four members of the security services, were killed when a vehicle rammed them on a street overnight into Tuesday. A police officer died in a separate incident.

Dozens of Khan supporters beat a videographer covering the protest for The Associated Press and took his camera. He sustained head injuries and was treated in a hospital.

By Tuesday afternoon, fresh waves of protesters made their way unopposed to their final destination in the Red Zone. Most demonstrators had the flag of Khan’s party around their shoulders or wore its tricolors on accessories.

Naqvi said Khan’s party had rejected a government offer to rally on the outskirts of the city.

Information Minister Atta Tarar warned there would be a severe government reaction to the violence. He said the government did not want Bushra Bibi to achieve her goal of freeing Khan. “She wants bodies falling to the ground. She wants bloodshed,” he said.

The government says only the courts can order Khan’s release. He was ousted in 2022 through a no-confidence vote in Parliament.

In a bid to foil the unrest, police have arrested more than 4,000 Khan supporters since Friday and suspended mobile and internet services in some parts of the country. Messaging platforms were also experiencing severe disruption in the capital.

Khan’s party relies heavily on social media and uses messaging platforms such as WhatsApp to share information, including details of events. The X platform, which is banned in Pakistan, is no longer accessible, even with a VPN.

Last Thursday, a court prohibited rallies in the capital and Naqvi said anyone violating the ban would be arrested. Travel between Islamabad and other cities has become nearly impossible because of shipping containers blocking the roads. All education institutions remain closed.

Pakistan's Stock Exchange lost more than $1.7 billion Tuesday due to rising political tensions, according to economist Mohammed Sohail from Topline Securities.

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Associated Press writers Munir Ahmed in Islamabad and Asim Tanveer in Multan, Pakistan, contributed to this report.