Pope Francis has condemned the Easter suicide bomb by Islamist militants that killed at least 70 people in Pakistan, many of them Christians, describing the attack as "hideous".

Addressing thousands of people in St. Peter's Square on Easter Monday, a religious holiday, the Pope demanded that the country's authorities protect religious minorities.

"Yesterday, in central Pakistan, Easter was bloodied by a hideous attack that massacred so many innocent people, mostly families of the Christian minority - especially women and children - gathered in a public park to enjoy the joy of the Easter holidays. I wish to express my closeness to all those affected by this vile and senseless crime, and invite you to pray to the Lord for the many victims and their loved ones," the Pope said.

"I appeal to civil authorities and all sectors of that nation to make every effort to restore security and serenity to the population, and in particular to the most vulnerable religious minorities," he added.

A breakaway Taliban militant group that once declared loyalty to Islamic State claimed responsibility for the blast.

The Pope, leading the large crowds in the square in a prayer for the victims and the minorities in the region, said violence only bred more violence and that respect and fraternity were key for promoting peace.

"I repeat, once again, that violence and murderous hatred only lead to pain and destruction. Respect and fraternity are the only way to achieve peace. May the Passover of the Lord inspire us even more to pray to God to stop the hands of the violent ones who sow terror and death and for love, justice and reconciliation to reign in the world. Let us all pray for those who died in this attack and their families and for the Christian and ethnic minorities in that region," he said.

Pakistan is a majority-Muslim state though it has a Christian population of more than two million.