According to the SITE Intelligence Group which monitors the extremist organisation's online activity, the IS directly released its own statement claiming it was behind the attack shortly afterwards, saying that the two suicide bombers detonated explosive belts in the church and a parking area in Jojo city, Sulu province – a stronghold of Islamic militants in the Catholic-majority nation.
The twin explosions happened after a mass at 8am (local time). The victims were mostly government troops and civilians.
The bombings took place days after the ratification of the Bangsamoro Organic Law (BOL), a new law that paves the way for the creation of a wider autonomous region for Muslim Filipinos in Mindanao.
Although Muslims overwhelmingly approved the law, Sulu province, where Jolo is located, voted against the autonomous government.
The Philippine Commission on Elections earlier said the law was ratified after getting more than 1.5 million favourable votes.