Several members of Pakistan’s security forces are reported to have been killed as supporters of jailed former Prime Minister Imran Khan forced their way into the capital, Islamabad.

Four security service personnel have been killed, the government said on Tuesday, as thousands defied a police lockdown, overcoming blockades and tear gas to enter the city. Supporters of Khan’s Pakistan Tehreek-e-Insaf (PTI) party have been demanding the ex-PM’s release ahead of a court hearing on terrorism charges.

Prime Minister Shehbaz Sharif’s office said in a statement that four members of the security services were killed when they were rammed by a vehicle.

As protesters battled security forces and ignored a government threat to respond with gunfire, Sharif condemned the violence, saying, “It is not a peaceful protest. It is extremism.”

The march into Islamabad follows two days of clashes as protesters approached the capital. The city administration had imposed a two-month ban on public gatherings last week.

Reports regarding the number of casualties vary. As well as the four security personnel, unconfirmed reports say that a civilian was also killed during the ramming and that a policeman has also died in a separate incident.

Policemen fire tear gas shells to disperse PTI supporters during a protest in Islamabad [Aamir Qureshi/AFP]

Al Jazeera’s Kamal Hyder, reporting from Islamabad, called the situation “extremely tense”.

“The protesters are now within the city. That is a point of great concern after the reports that the police were to crush the protests,” he said.

Hyder noted contradictory reports about the deaths.

“The government is saying that it was the protesters who ran over those security forces personnel, but witnesses said that it was the security forces vehicle speeding away in panic when the protesters were closing in,” he said.

Khan, who was ousted in 2022 through a no-confidence vote, has been in jail for more than a year following his conviction in a corruption case and faces more than 150 criminal cases.

His PTI party says the cases are politically motivated, while authorities say only the courts can order his release.

Police have arrested more than 4,000 Khan supporters since Friday and suspended mobile and internet services in some parts of the country. All educational institutions remain closed.

On Thursday, a court prohibited rallies in the capital, and authorities said anyone violating the ban would be arrested.

Travel between Islamabad and other cities has become nearly impossible, with the authorities blocking roads with shipping containers. However, the protesters pushed them aside on Tuesday.