Pakistan's opposition parties gathered in the capital, Islamabad, on Tuesday night for a major anti-government rally to demand that Prime Minister Imran Khan step down.
The parties, led by the Pakistan People's Party, have accused Mr Khan of mismanaging the economy.
“Resign in 24 hours and face us in an election, or be prepared for a no-confidence move,” PPP leader Bilawal Bhutto Zardari, son of assassinated former prime minister Benazir Bhutto and former president Asif Ali Zardari, told the rally.
Protesters first assembled in the eastern city of Lahore on Sunday and took to the road.
By Tuesday, they set out at noon in hundreds of cars and buses from Rawat, a town in Punjab province, and reached the outskirts of Islamabad hours later.
“The no-confidence motion against the prime minister is the democratic weapon of this crowd. We always understand that democracy is the best revenge,” Mr Zardari said.
“So, what better revenge could there be? The puppet [referring to the prime minister] was imposed on us, imposed on this nation, imposed on Pakistan. So, we are using our democratic right to send back this prime minister.”
Pakistani opposition parties often hold such rallies, but this one follows a formal no-confidence motion against Mr Khan that was submitted to parliament by the opposition, led by the PPP.
The formal request requires Mr Khan to seek a parliamentary vote of confidence.
Should Mr Khan fail to win approval, the parliament will have to choose a new prime minister.
Mr Khan has remained defiant, claiming he still enjoys the backing of the majority of politicians.
“Whatever they do, I am ready for that,” he told a gathering in Islamabad.
The opposition needs a simple majority of 172 and says it requires only 11 more votes to force the prime minister out.
Mr Khan won a confidence vote last year by six votes.
Under the country's constitution, the speaker of the National Assembly now must convene a special session that will deliberate whether the prime minister still has majority support in the house.
Mr Khan, a former cricket star turned politician, came to power in 2018 but his popularity has declined since last year, due to increasing inflation and depleting foreign reserves.