Thousands of protesters have clashed with police in Islamabad in the second day of protests over blasphemy laws in Pakistan.

Demonstrators gathered outside Parliament and other key buildings to demanding authorities implement Sharia, or Islamic law.

As many as 25,000 protesters occupied the high-security zone in Islamabad to press their demands, with some setting fire to cars. The army was deployed on Sunday to contain the rioters.

Demonstrators marched from the garrison town of Rawalpindi to Islamabad in protest at the execution of Mumtaz Qadri, who some hard-line Muslims consider a hero for murdering Punjab province governor Salman Taseer.

Supporters of executed Islamist Mumtaz Qadri shout slogans as they sit-in during an anti-government protest in front of the parliament building in Islamabad on 28 March, 2016 (AFP/Getty)

In January 2011, Qadri shot Mr Taseer 28 times for defending a Christian woman jailed on blasphemy charges.

Mr Taseer had criticised Pakistan's harsh blasphemy laws after Aasia Bibi was sentenced to death for allegedly insulting Islam and promoting her own faith.

Qadri told police he had killed the governor because he had spoken out against the blasphemy laws - at the time of the murder, thousands took to the streets in support of Qadri's views.

Supporters of the religious party Sunni Tehreek chant slogans during a sit-in protest near the parliament building in Islamabad, Pakistan, Monday, 28 March, 2016. (AP)

In recent weeks, Pakistan's Islamist parties have been threatening widespread demonstrations to protest what they say is Prime Minister Nawaz Sharif's pro-western stance.

Earlier this month, the prime minister officially recognised holidays celebrated by the country's minority religious - the Hindu festival of Holi and the Christian Easter.

They have also denounced draft legislation in Punjab outlawing violence against women.

A breakaway Taliban faction, which publicly supports Isis, claimed responsibility for a suicide bomb attack targeting Christians gathered for Easter.

At least 72 people - including 29 children - were killed in the attack on Sunday when the bomber struck in a busy park in the eastern city of Lahore, the power base of Prime Minister Nawaz Sharif.

Pope Francis condemned the attack as "hideous" and demanded that Pakistani authorities protect religious minorities.