Pakistani protesters demanding the release of ex-prime minister Imran Khan on Tuesday killed four members of the nation's security forces, the government said, as the crowds defied police and closed in on the capital's centre.
Convoys of pro-Khan demonstrators have been marching on Islamabad since Sunday, hauling aside roadblocks and skirmishing with police and paramilitary forces firing volleys of rubber bullets and tear gas.
Khan has been jailed since last summer, sidelined by dozens of legal cases he claims were confected to prevent his comeback in February elections marred by rigging allegations.
Since the vote his Pakistan Tehreek-e-Insaf (PTI) party has defied a government crackdown with regular rallies, but Tuesday's is by far the largest to grip the capital since Khan's incarceration.
Despite a ban on public gatherings, news agency AFP reported saw more than 10,000 protesters in the city centre.
Some were armed with sticks and slingshots, just one mile (1.6 kilometres) away from a square in the government enclave they aim to occupy.
"This is not our government, this government is made up of traitors," protester Abdul Rashid told AFP, his face covered by a thick scarf. "Long live Imran Khan."
The government said rioters killed four members of a state paramilitary force, running them over with a vehicle on a city highway leading to the government sector.
One police officer was also reported killed in unrest on Monday.
There was no immediate official figure available for any casualties among the demonstrators.
"These disruptive elements do not seek revolution but bloodshed," Prime Minister Shehbaz Sharif said in a statement. "This is not a peaceful protest, it is extremism."
The capital has been locked down since late Saturday, with mobile internet sporadically cut and more than 20,000 police flooding the streets, many armed with riot shields and batons.
"The state's response is completely unwarranted and disproportionate. We have the right to protest," PTI lawmaker Waqas Akram told AFP by phone.
"They treat their own people as enemies," he said.
The government has accused protesters of attempting to derail a state visit by Belarusian President Alexander Lukashenko, who arrived for a three-day trip on Monday.
"Nobody will be allowed to disrupt the visit," Information Minister Attaullah Tarar told reporters.
Last week, the Islamabad city administration announced a two-month ban on public gatherings.
But PTI convoys travelled from their power base in northwestern Khyber Pakhtunkhwa province and the most populous province of Punjab.
The government cited "security concerns" for the mobile internet outages, while Islamabad's schools and universities were also ordered shut on Monday and Tuesday.
Amnesty International said "as protesters enter the capital, law enforcement officials have used unlawful and excessive force".
The rights organisation said there had been "a grave violation of the rights to freedom of peaceful assembly, movement and expression", in a statement posted on social media platform X.
PTI's chief demand is the release of Khan, the 72-year-old charismatic former cricket star who served as premier from 2018 to 2022 and is the lodestar of their party.
They are also protesting alleged tampering in the February polls and a recent government-backed constitutional amendment giving it more power over the courts, where Khan is tangled in dozens of cases.
Sharif's government has come under increasing criticism for deploying heavy-handed measures to quash PTI's protests.
"It speaks of a siege mentality on the part of the government and establishment -- a state in which they see themselves in constant danger and fearful all the time of being overwhelmed by opponents," read one opinion piece in the English-language Dawn newspaper published Monday.
"This urges them to take strong-arm measures, not occasionally but incessantly."
Khan was ousted by a no-confidence vote after falling out with the kingmaking military establishment, which analysts say engineers the rise and fall of Pakistan's politicians.
But as opposition leader, he led an unprecedented campaign of defiance, with PTI street protests boiling over into unrest that the government cited as the reason for its crackdown.
PTI won more seats than any other party in this year's election, but a coalition of parties considered more pliable to military influence shut them out of power.