Gunman fatally shot several people in a series of attacks on churches, a synagogue and a police post in Russia's southern republic of Dagestan, officials said on Monday.
The governor of Dagestan, Sergei Melikov, said at least 15 police officers were killed in the clashes. He said civilians had also been killed in the attacks, but did not give a number.
He described the shootings, which occurred on Sunday evening in the cities of Derbent and Makhachkala, as an attempt to destabilize the region. The two cities are about 100 kilometres apart.
Russia's National Anti-Terrorism Committee said they opened criminal proceedings and that the counter-terrorism operation has ended "because the threat to the life ... of citizens has been eliminated."
On Sunday evening, unknown assailants opened fire on synagogues and churches in Dagestan's regional capital Makhachkala and the city of Derbent, in what appears to be coordinated attacks.
The synagogue in Derbent went up in flames. It took hours to extinguish the fire. An Orthodox priest was killed in a church. A police station was also targeted.
Muslim-majority Dagestan, located in the North Caucuses, is one of the poorest regions in Russia. It borders Chechnya.
The authorities immediately launched a manhunt and shut routes out of Makhachkala. It was later reported that the gunmen were successfully blocked. According to officials, five attackers were killed.
The exact motive behind the attacks remains unclear - no group has yet claimed responsibility.
Some politicians in Dagestan and Moscow have blamed Ukraine.
In response to the attacks, Dagestan has declared three days of mourning.