Over 25,000 supporters of opposition leader Imran Khan and cleric Tahir-ul-Qadri vowing not to back down till Prime Minister Nawaz Sharif resigns and dissolves Parliament and provincial assemblies, poured into the streets of Pakistan's capital, posing the biggest challenge to the 15-month-old civilian government.
Unfazed by the country's apex court's order against any unconstitutional step to topple the government, the two opposition groups held separate sit-ins, demanding Sharif's resignation and fresh polls alleging rigging during the last year's elections.
Khan, who had left the protest venue to rest at his house in Bani Gala area of Islamabad, came out later to join his supporters waiting for hours at the protest venue.
"I am going to the venue and will not come back till Sharif resigns," Khan, who heads the Pakistan Tehreek-e-Insaaf (PTI) told reporters.
Earlier, addressing thousands of supporters who were part of his 'Azadi March' from Lahore that finally reached the capital at 4 am after starting off on Thursday, Khan announced to stage a sit-in in the capital from 3 pm today till Sharif resigns.
"I am not derailing democracy because there is no democracy in the country. We will not go away till Nawaz Sharif resigns," Khan told his supporters.
As Khan spoke, senior party leaders and workers chanted the slogan of "Go Nawaz Go".
The rain and the over 300 km journey took a toll on Khan's health as he was down with fever. He had not slept for over 40 hours.
"The time has arrived when the nation should decide. I will stay here until the Prime Minister resigns. We don't accept a Prime Minister who has been appointed after rigged elections," Khan said.
"We went to the election commission and the Supreme Court against the rigging in the elections. When we could not get justice, then we decided that there is no other way but to come on roads to get justice," he said.
In the 2013 general elections, Sharif had won by a landslide, taking 190 out of 342 seats. Khan's PTI got 34 seats, the third largest bloc in the legislature. But he claimed his party should have had many more seats.
Meanwhile, thousands of supporters of Pakistan Awami Tehreek (PAT) camping in an adjacent street was addressed by the Canada-based cleric, who demanded the arrest of Sharif and Punjab Chief Minister Shahbaz Sharif over the killing of 14 of his supporters in a clash with police in Lahore on June 17.
"I will not leave until Nawaz, Shahbaz are arrested," Qadri said.
"Nawaz, (his younger brother) Shahbaz should resign and murder cases should registered against them for killing of our 14 workers in Lahore on June 17," Qadri said.
He said a case is being registered against Sharif and Shahbaz over the Model Town incident.
"Now it is up to police to either follow the due process and register an FIR or suffer the consequences," Qadri said.
In his seven-point charter of demands, the cleric also called for the dissolution of the national and provincial assemblies.
He also demanded formation of a national government which works on the project of thorough democratic reforms in the country.
Qadri also offered a 10-point social programme of free education, health, jobs, housing etc after the formation of national government. His followers committed themselves to not leave the venue till his revolution.
Earlier, ahead of arriving in Islamabad, Qadri promised that his 'Revolution March' will be peaceful.
Riot police have cordoned off two streets in downtown Islamabad with shipping containers and barbed wire for the protests.
The political instability comes at a time when Pakistan is waging a war against militants -- particularly in the restive tribal regions along its border with Afghanistan.
Pakistan Supreme Court had yesterday issued an order against any unconstitutional step to remove the civilian government as protests threatened to remove government which sparked fears of a possible military intervention in the coup-prone country.
The Army which has already been handed over the security of capital for three months, has a history of capturing power from democratically elected governments.
In its 67-year history, Pakistan has witnessed three coups, including one against Sharif in 1999 by the then army chief General Parvez Musharraf.
The Government expects the marchers disperse peacefully as backdoor efforts are already going on to meet some of the demands of Khan and Qadri.
Yesterday, as the march led by Khan passed through the city of Gujranwala, clashes erupted between his convoy and supporters of Sharif's Pakistan Muslim League-N after shots were fired at Khan's vehicle.
Sharif, on last Tuesday, had announced appointment of a panel of three judges of the Supreme Court to probe the charges of fraud in the elections.
The government has deployed thousands of police and paramilitary soldiers to maintain law and order.