"Three martyrdom attacks killed 11 and wounded at least 41 among church guards and Christians," it said via the Telegram messaging app.
The jihadist group's toll tallied with that of police following the seemingly coordinated attacks against three churches in the city of Surabaya at around 7.30am local time (00.30GMT).
IS has claimed responsibility for several recent attacks in Indonesia, most of them carried out by its affiliate Jamaah Ansharut Daulah.
In January 2016, IS claimed a gun and suicide attack in the capital Jakarta that left four attackers and four civilians dead.
In May last year, suicide attacks which killed three policemen and wounded a dozen more at a busy Jakarta bus station were also claimed by IS.
Days ago, a prisoner and five police officers were killed in clashes at a high-security jail during which Islamist inmates took an officer hostage.
IS said it was behind the riot, a claim authorities rejected.
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