Women and men from majority Muslim areas of Russia, including Chechnya, have traveled to Syria and Iraq to fight alongside the Islamic State there, and dozens have begun to return as the group has lost most of its territory.

The restive region of Chechnya was the site of two separatist wars in the 1990s. Following those conflicts, Mr. Kadyrov, with the backing of the Russian government, has cracked down on dissent. Human rights groups have accused his forces of abuses including torture, kidnapping and murder.

Grozny once had a substantial ethnic Russian, Christian population but most of them fled during the wars. The church that was attacked Saturday is in the center of the city and was at the heart of some of the battles of the 1990s.

Mr. Kadyrov condemned Saturday’s assault and said he immediately went to the church and was with the police as they responded. He vowed to crush anyone who attempted attacks in his region.

“I once again very seriously declare that you can try to commit any actions aimed at undermining the security of the residents of Grozny and other settlements,” he said. “But anyone who makes the first step along this path will be immediately destroyed.” He made the statement via the Telegram messaging app, where he regularly posts information after being kicked off both Instagram and Facebook after he was added to a United States sanctions list.