The group claimed a suicide bombing that targeted a in the Pakistani city of Peshawar on Friday, killing at least 56 people.
"Today Friday, an Islamic State fighter succeeded in assaulting a Shia mosque in Peshawar," in northwestern , the transnational militant group said on its Amaq propaganda site.
The deadly bombing came on the first day of a cricket Test match in Rawalpindi -- around 190 kilometres (120 miles) to the east -- between Pakistan and Australia, who have not toured the country in nearly a quarter of a century because of security concerns.
Pakistan Information Minister Fawad Chaudhry said in a statement that three investigation teams were established to study forensic evidence and closed-circuit TV footage to track down the attack's organisers.
The Taliban rulers in Afghanistan, who have been fighting IS, condemned the attack. IS has proven to be the Taliban's greatest security threat since sweeping into power last August.
“We condemn the bombing of a mosque in Peshawar, Pakistan. There is no justification for attacking civilians and worshipers," Taliban Deputy Minister for Culture and Information Zabihullah Mujahid tweeted. He refused to comment on the IS claim that the suicide bomber was Afghan.