At least one policeman was killed and dozens on both sides wounded as supporters of jailed former prime minister Imran Khan clashed with security forces outside Pakistan's capital Islamabad yesterday, a government minister and Khan's party said.

Authorities have enforced a security lockdown for the last two days to block the PTI protesters, whom Khan has called on to march on parliament for a sit-in demonstration to demand his release, while highways into the city have been barricaded.

The government has used shipping containers to block major roads and streets in Islamabad, most of them patrolled by large contingents of police and paramilitary personnel in riot gear.

Officials and witnesses said all public transport between cities and terminals had also been shut down in the eastern province of Punjab to keep away the protesters, led by members of Khan's Pakistan Tehreek-e-Insaf (PTI) party.

"We wouldn't let them storm the capital," said provincial Information Minister Uzma Bukhari, adding that about 80 of Khan's supporters had been arrested.

One police officer was shot and killed and at least 70 others were wounded in clashes with the protesters just outside Islamabad, she told a press conference. There were reports of several other clashes elsewhere in the province, she said.

Khan's party said scores of its workers were also hurt.

The capital added an extra layer of security ahead of a visit by the President of Belarus, Aleksandr Lukashenko, yesterday.

Khan's party accused the government of using violent tactics to block the protesters, saying it had arrested hundreds of workers and leaders.

"They are even firing live bullets," one of Khan's aides, Shaukat Yousafzai, told broadcaster Geo News TV.

Gatherings of any sort in Islamabad have been banned, police said in a statement. Authorities closed all schools in Islamabad and the adjacent garrison city of Rawalpindi, while the internet and WhatsApp messaging services also slowed.

The protest march, which Khan has described as the "final call", is one of many his party had held to seek his release since he was jailed in August last year. The party's most recent protest in Islamabad, early in October, turned violent.

Khan's third wife, Bushra Bibi, and a key aide, Ali Amin Gandapur, who is the chief minister of Khyber Pakhtunkhwa province, are leading a march that arrived just outside Islamabad on Sunday night, his party said.

Voted out of power by parliament in 2022 after falling out with Pakistan's powerful military, Khan faces charges ranging from corruption to instigation of violence, all of which he and his party deny.