A Russian official pointed to Islamic "sleeper cells" after gunmen carried out coordinated attacks on synagogues and churches in two cities in the southern region of Dagestan, killing at least 20 people Sunday.
In the assault, an Orthodox priest’s throat was slit, and at least three other civilians and 15 police officers were killed.
The Dagestani regional governor visited the site of a weekend attack by Islamist militants, which killed 20 and injured another 26.
A deadly attack by gunmen in the majority Muslim region of Dagestan just months after the assault on a Moscow concert hall is raising the spectre that Russia may be facing a wave of violence by religious extremists.