A suicide attack at a hospital in Pakistan that killed at least 70 people on Monday has been condemned as an "inhuman act" by the Catholic Church in the country.

The National Commission for Justice and Peace, part of the Catholic Bishops' Conference in Pakistan, released a statement branding the blast a "tragic killing".

"Killing innocent people is [an] inhuman act and totally unacceptable," the statement said.

The attack took place at a government hospital in the southewestern city of Quetta. According to medical staff, up to 60 of those killed were lawyers who were there to mourn the death of the president of the Baluchistan Bar Association, Bilal Anwar Kasi, who had been assassinated earlier on Monday by gunmen while on his way to court.

Two Islamist groups, Islamic State and Jamaat-ul-Ahrah, a faction of the Pakistani Taliban, have both claimed responsibility for the blast. However, according to Reuters, analysts say ISIS' claim is "unconvincing".

International affairs director of the World Council of Churches, Peter Prove, on Monday offered prayers and condolences to the families of the victims.

"Deliberately attacking people gathered at a hospital to grieve for Mr Kasi underscores the inhumanity and moral bankruptcy of those who planned and perpetrated it," Prove said.

"This atrocity, as so many before it, demands denunciation by all people of faith, good will and simple decency, and prayers and support for the families and communities affected, and for the people and nation of Pakistan."

The Church of England also offered a prayer for peace in Pakistan:

Pakistani lawyers have today launched a nationwide strike in response to the attack, urging the government to increase protections.