An influential Pakistani preacher and thousands of his supporters have reached Islamabad on Monday as part of a "long march" against corruption.
Tahirul Qadri, a preacher who returned to Pakistan from Canada last month, is leading a call for electoral reforms.
He left the city of Lahore on Sunday with thousands of supporters, and reached Islamabad late on Monday, where he addressed crowds near parliament.
The authorities accuse him of trying to postpone elections due by May.
The cleric wants the military and judiciary to be involved in installing a caretaker government to oversee the forthcoming elections.
The government is due to disband in March, and elections must then be held within six weeks.
Addressing tens of thousands of supporters in the capital late on Monday night, Mr Qadri called for provincial assemblies to make way for a caretaker administration.
He wants measures put in place to prevent corrupt people or criminals from standing for elected office.
"Morally, your government and your assemblies have ended tonight," he said from behind bullet-proof glass on a stage erected on Jinnah Avenue, less than a mile from Pakistan's parliament.
"I will give [the government] a deadline until tomorrow to dissolve the federal parliament and provincial assemblies. After that, the people's assembly here will take their own decision."
Earlier, his black chauffeur-driven car was showered with pink rose petals as it approached the stage in Pakistan's main city.
By the time his procession reached Islamabad, an estimated 10,000 people had joined the slow-moving convoy of cars, buses and trucks - more crowds were waiting in Islamabad to greet the cleric.
An extra 15,000 police had been deployed on the streets and many parts of the capital were sealed off.
Authorities in the capital had warned that Mr Qadri and his supporters would not be allowed into the city centre. The government had warned that militants may target the marchers.
Mr Qadri's flamboyant preaching style and expensive television campaigns have raised his profile in Pakistan in recent weeks.
But there has also been widespread speculation that he is backed by Pakistan's powerful military, and is being used to reassert the army's control over Pakistani politics.
Mr Qadri has rejected this allegation. "I have no link with military institutions," he told Reuters. "I am one of the biggest staunch believers... of democracy in the whole world."
He was a prominent supporter of former army chief Pervez Musharraf when he seized power in a coup in 1999, and served in the national assembly under him before moving to Canada in 2006, where he ran a charity.
In December he was able to mobilise tens of thousands of supporters at a rally in Lahore, but it remains unclear how much support he enjoys across the country.