Thousands of protesters gathered in the Pakistani city of Lahore on Thursday, preparing to march on the capital to unseat the government they claim was elected by fraud.
Supporters of cricketer-turned-politician Imran Khan and populist preacher Tahir-ul-Qadri massed separately ahead of the planned rally in Islamabad, 300 kilometres (190 miles) away.
Both Khan and Qadri say the last general election was rigged, and want Prime Minister Nawaz Sharif to resign and hold new polls. Sharif won by a landslide in May 2013.
The authorities have indicated they will allow Khan, whose Pakistan Tehreek-e-Insaaf (PTI) political party came third in the polls, to go ahead with his march.
But Rana Mashhood, the law minister for Punjab government, of which Lahore is the capital, told AFP they would not permit Qadri's protest -- and were seeking the cleric's arrest.
"We are resolved to curtail their activity because of their violence and attacks on police during the past few days," Mashhood said.
Security in Islamabad and on its approach roads has been ramped up in recent days.
More than 20,000 police and security forces have been deployed and almost all roads into the city have been blocked by the authorities with barbed wire and shipping containers.
Flags and barricades
Qadri's Pakistan Awami Tehreek (PAT) group complained of government "double standards", saying they were being penned in around their leader's home in Lahore while PTI were being given free rein to carry on their protest.
PAT spokesman Qazi Faiz-ul-Islam told AFP they were determined to break the barricades to complete the journey to Islamabad.
Qadri followers clashed with police last week when they tried to remove blockades around the cleric's residence, leaving at least two people dead, and there were fears of more violence on Thursday.
An AFP journalist saw PAT supporters equipping themselves with clubs, masks and helmets in preparation for the march.
There was a festive mood in Lahore's Zaman Park where thousands of PTI supporters gathered, waving green and red party flags, dancing and singing patriotic songs.
Khan urged his followers on, galvanising them into action.
"If you succeed, then there will be justice in Pakistan and people all around the world will respect the green passport," Khan told the cheering crowd.
Khan, a cricket hero who led Pakistan to World Cup glory in 1992, has persistently cried foul over last year's election and tried numerous avenues to have the results of a number of seats thrown out.
But international observers who monitored the polls said they were free and credible and critics say PTI should not have accepted their seats in parliament if they did not believe the vote was fair.
The "long march" planned for Thursday, the anniversary of Pakistan's independence from Britain, will in fact be a motorised cavalcade, and is unlikely to reach Islamabad before the evening.
Some have accused PTI and PAT of being aided by the powerful military establishment to undermine the government, diverting attention from more pressing issues like an offensive against the Taliban in the northwest and the country's economy.
On Monday Qadri told AFP he wanted an "interim national government" consisting of technocrats and experts.
Political analyst and author Imtiaz Gul said the protests were one of the biggest challenges Sharif has faced since being elected for a third stint in office last year.
In a country which has seen three coups in its 67-year history, the threat of army intervention always hovers in the background at times of unrest.
But while Gul said there was a "real danger of bloodshed and violence", he added a coup was unlikely, though the coming days could leave the civilian government weakened.
"Based on the past experiences and in view of the the current national and international environment, the army will not possibly intervene," he said.
"However it may still use its political clout to nudge the politicians away from confrontation."
The military is rumoured to be unhappy with the way the Sharif government has pursued criminal charges, particularly a treason case, against former army chief Pervez Musharraf.
A four-day sit-in protest Qadri led in central Islamabad in January last year, aimed at bringing down the last government and getting a caretaker administration to enact reforms, sparked fears of a plot to derail the general election.