An explosion at a packed Shiite mosque in Pakistan has killed at least 40 people. There are reports that the death toll may be as high as 49.

More than fifty were wounded in the attack in the southern city of Shikarpur during Friday prayers.

A Sunni militant group has claimed responsibility. Local media has claimed the attack may have been a  suicide bombing, but police are still investigating.

Radical Sunni groups see Shiite Muslims as kafirs – or infidels – and frequently target Shiite populations. Earlier this month a suicide bomber killed six and wounded 17 at a Shiite mosque in the city of Rawalpindi.

Jundullah, a group which has broken away from the Pakistani Taliban and has pledged support for Islamic State in Iraq and Syria, has claimed responsibility, Reuters reports.