Here are the latest developments in this story:
The protesters, wearing masks and carrying makeshift shields, hammered through barbed wire and locks connecting the shipping containers which the authorities had used as makeshift roadblocks. And they had brought cranes that were used to move the containers. (See Pics)
Mr Khan, who leads the Pakistan Tehreek-e-Insaaf, and preacher Tahir-ul-Qadri claim last year's general election, in which Prime Minister Nawaz Sharif's Pakistan Muslim League-N had won a landslide victory, was rigged. The election was rated as free and credible by international observers. (Buzz on Twitter)
Mr Sharif has refused to step down. In a move to underscore the Army's support to his government, he has also deployed 700 soldiers to guard the Red Zone, which houses key buildings including Parliament, the prime minister's house and numerous Western embassies.(Pakistan Army Urges Dialogue to Resolve Political Crisis)
But despite fears of violence, there were no major clashes. The government had pledged restraint and the soldiers turned spectators as women and children, who took part in the protest, marched on.
"PM just told me he has ordered the police not to use any kind of force against the protesters as women & children are in the front rows," Mr Sharif's daughter Maryam Nawaz Sharif tweeted.
In their turn, both Mr Khan and Mr Qadri had asked the protesters to maintain peace. "We will protest in front of the Parliament, we will stage such a big crowd that people will forget Tahrir Square," Mr Khan told his followers. "When injustice becomes law, resistance becomes duty. Yesterday we took a giant step 4 Naya Pakistan & democracy.." he tweeted this morning.
Nuclear-armed Pakistan has experienced three military coups and Mr Khan's protest raises fears of the army stepping in. Thus, opposition parties had shunned Mr Khan's call to unseat the government and urged him to come to the negotiating table.
The International community, too, has signalled its displeasure. Britain, one of Pakistan's leading partners and a major aid donor, has urged the two sides to find a democratic solution to the crisis. The European Union also voiced its support for democracy in Pakistan - and linked it to a highly prized trade deal.
Mr Sharif has done his best to pre-empt the protests. Last week, he proposed setting up a judicial commission to probe the allegations of rigging, but Mr Khan dismissed the proposal. The government has already set up a parliamentary committee to look at electoral reforms.
As of now, the trouble shows no sign of abating. Mr Khan has warned that if Mr Sharif does not resign by Wednesday evening, he would lead his supporters to the prime minister's official residence.
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