The Pakistani capital Islamabad was put under a security lockdown on Sunday as supporters of jailed former Prime Minister Imran Khan demonstrated for his release.

The protesters are demanding Khan's release, as well as other members of the Pakistan Tehreek-e-Insaf (PTI) party, and the resignation of the current government, due to what they say was a rigged election.

The Associated Press reported that police arrested thousands of Khan supporters, including five parliamentarians, citing a security official with the information.

The country suspended mobile and internet service in "areas with security concerns" in response to the protests. 

Highways leading to Islamabad were blocked where PTI supporters were expected to approach the city from the provinces of Punjab and Khyber Pakhtunkhwa.

In the eastern city of Lahore, police arrested PTI members while bystanders tried to make their way through blockades. 

Gatherings of any sort have been banned under legal provisions, local police said in a statement.

Ali Amin Gandapur, chief minister of Khyber Pakhtunkhwa province and a key Khan aid, called on people to gather near the entrance to the city's red zone, known as "D Chowk."

"Khan has called on us to remain there till all our demands are met," he said in a video.

Islamabad braces for violence

The Pakistani government took similar measures ahead of expected protests by Khan supporters in October. Back then, the protest turned violent, with one policeman killed, dozens of security personnel injured and protesters arrested.

Both sides accused each other of instigating the violence.

Khan, who was ousted from power by a no-confidence vote in April 2022, has been serving a three-year jail sentence since 2023.

Despite facing some 150 criminal cases against him, including being accused of corruption and instigation of violence, he remains a popular figure in Pakistani politics, with his supporters saying the allegations are politically motivated.

Khan was granted bail last December, but he remained behind bars due to the various other legal troubles he has been facing since his 2022 ousting.

Both he and his party deny all the charges.

ftm/ab (Reuters, AP)