At least 43 people were killed and around 100 injured on Saturday in a bombing at a Sufi Muslim shrine in Pakistan's Balochistan province.
The explosion took place at the Shah Norani shrine in Balochistan's Lasbella district.
According to details, the blast occurred when "dhamaal" was taking place in the shrine.
The IS claimed responsibility for the attack in a statement, saying a "gathering of apostates" had been targeted, whose authenticity could not be confirmed, Efe news agency reported.
Spokesman for the Balochistan provincial government Anwar ul-Haq Kakar said that women and children were among the casualties.
Kakar said a complicated operation was underway to transfer the injured from the mountainous area where the shrine is located to the nearest hospitals.
He said there were no strict security measures in place because the site of the attack was typically peaceful.
Pakistan has experienced a significant reduction in extremist violence since June 2014, when an armed forces operation was launched in tribal areas against Tehrik-i-Taliban Pakistan, or TTP, and other insurgent groups.
In October 2016, heavily-armed militants wearing suicide vests stormed a police academy in Quetta, killing at least 61 people and wounding at least 117.
The attack was carried out by Al-Alimi faction of the Lashkar-i-Jhangvi (LJ) militant group.