Islamist protesters gathered in the Pakistani capital said Wednesday they would not end their days-long sit-in and were "willing to die", as armed security forces readied to clear the camp.

The stand-off, which comes as Pakistan mourns more than 70 people killed in a Taliban suicide bombing targeting Christians celebrating Easter Sunday in Lahore, underscores deep religious divisions fuelling the Muslim country's long battle with extremism. 

Several thousand protesters marched on Islamabad Sunday, clashing with security forces before setting up camp outside key government buildings along the capital's main Constitution Avenue.

The protestors -- who numbered some 25,000 at their peak -- had gathered in support of Mumtaz Qadri, who was hanged in late February five years after he assassinated a liberal Punjab governor over his calls to reform the country's blasphemy laws.

The government gave the demonstrators an ultimatum to leave late Tuesday, but it went unheeded, prompting the government to issue a second call saying security forces would begin an operation to clear the area Wednesday morning.

"If the protesters do not disperse peacefully tonight, then we will evict them in the morning in front of everyone," Interior Minister Chaudhry Nisar Ali Khan told reporters late Tuesday.

Protesters were calm Wednesday morning as leaders said they were holding talks with authorities.

"We won't move from this place until and unless all 10 demands are accepted," said protest leader Ashraf Asif Jalali.

"Our workers are willing to die. If the government takes action they will not run away but face the bullets. They are not armed with guns but with clubs."

A police source said more than 7,000 security forces were poised to clear the sit-in, including the paramilitary Rangers and Frontier Corps with reinforcements from the Punjab police.

Army troops are already standing guard at government buildings near the protest camp.

 Qadri's legacy

 Hailed as a hero by right-wing religious groups when he murdered Punjab governor Salmaan Taseer, the demonstrators have demanded that Qadri be named a "martyr" and called for the execution of Asia Bibi, a Christian mother of five on death row for blasphemy.

They have also demanded the imposition of Sharia law.

The government has so far rejected their demands.

Qadri's hanging, hailed as a "key moment" by analysts in Pakistan's war on religious extremism, has become a flashpoint for the deep divisions in the conservative Muslim country.

His funeral earlier this month drew tens of thousands in an extremist show of force that alarmed moderate Muslims in the country, while the call to hang Bibi along with the Easter attack in Lahore has underscored a growing sense of insecurity for Pakistan's minorities.

"It's a sense of great grief, sorrow and fear," Shamoon Gill, spokesman for the All Pakistan Minorities Alliance, told AFP. 

The Lahore blast had left Christians feeling that "no place is safe", he said, while the "mob situation" in Islamabad was "dangerous".

"They are a serious threat to Asia Bibi's life... there is a chance the government could bow down to pressure on this issue," he warned.

Moderate Muslims are also set to suffer by growing religious extremism, he said, calling on the government to devise a "clear strategy".