The prime minister of Pakistan has vowed to eliminate perpetrators of terror attacks such as the suicide bombing in Lahore that targeted Christians gathered for Easter, killing 70 people.

A breakaway Taliban faction, which publicly supports the so-called 'Islamic State' group, has claimed responsibility for the attack.

In the capital of Islamabad, extremists protested for a second day outside Parliament and other key buildings in the city centre.

The demonstrators set cars on fire, demanding that authorities impose Islamic law or Sharia.

The army, which was deployed Sunday to contain the rioters, remained out on the streets.

After a meeting with his security officials today, Prime Minister Nawaz Sharif called the perpetrators of the Lahore attack "cowards" and vowed to defeat the "extremist mindset".

He also cancelled a planned trip to Great Britain.

The military reported raids in eastern Punjab province, where several deadly militant organisations are based, and said dozens were arrested as Pakistan started observing a three-day mourning period declared after the attack.

The Lahore bombing took place in a park that was crowded with families, with many women and children among the victims. At least 300 people were wounded in the bombing.#

Even though a breakaway Taliban group, known as Jamaat-ul-Ahrar, said it specifically targeted Pakistan's Christian community, most of those killed in Lahore were Muslims, who were also gathered in the park for the Sunday weekend holiday.

The park is a popular spot in the heart of Lahore.

Of the dead, 14 have been identified as Christians and 44 as Muslim, according to Lahore Police Superintendent Mohammed Iqbal.

Another 12 bodies have not yet been identified, he said.

Ahsanullah Ahsan, a spokesman for the breakaway Taliban faction, told the Associated Press that along with striking Christians celebrating Easter, the attack also meant to protest Pakistan's military operation in the tribal regions.

The same militant group also took responsibility for the twin bombings of a Christian Church in Lahore last year.

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

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

Mr Sharif had earlier this month officially recognised holidays celebrated by the country's minority religions, the Hindu festival of Holi and the Christian holiday of Easter.

In Lahore, dozens of families were bidding final farewell to their slain kin during funeral ceremonies.

Shama Pervez, widowed mother of 11-year-old Sahil Pervez who died in the blast, was inconsolable during funeral prayers. Her son had pleaded with her to go to the park rather than stay home on Sunday, and she said she finally gave in.

Ten members of Qasim Ali's family were killed in the park, all Muslims.

His 10 year-old nephew Fahad Ali lay in a bed in his home, his battered body almost completely damaged. He had lost his parents and a sister, another two sisters were badly injured.

"I don't know how I will be able to do anything, to continue at school," he cried.

Forensic experts sifted through the debris in the park.

The suicide bomb had been a crude device loaded with ball bearings, designed to rip through the bodies of its victims to cause maximum damage, said counter-terrorism official Rana Tufail.

He identified the suicide bomber as Mohammed Yusuf, saying he was known as a militant recruiter.

In Turkey, President Recep Tayyip Erdogan condemned the Lahore bombing, saying that in targeting a park filled with children, the attack "revealed the face of terror, which knows no limits and values".

France expressed its "solidarity in these difficult moments" to the authorities and the people of Pakistan and underlined "the inflexible will of our country to continue to battle terrorism everywhere."