At least 21 people, 16 policemen and 5 civilians including a priest, died this Sunday in several attacks on police posts, orthodox churches and a synagogue, in Russia's southern region of Dagestan.

There were also at least 46 people wounded who taken to the hospital, and authorities have declared three days of mourning.

No group has yet claimed responsibility for the attacks, the deadliest in Russia since March, when gunmen opened fire at a concert in Moscow, killing 145 people.

The group that claimed responsibility for that raid, praised the attack in Dagestan, stating it was led by “brothers in the Caucasus who showed that they are still strong”.

Two Orthodox churches, a synagogue and a police post

Russian media reported that around 6:00 pm local time on Sunday, gunmen entered in an Orthodox church and a synagogue in the city of Derbent, and opened fire with automatic weapons.

Rev. Nikolai Kotelnikov, the 66-year-old Russian Orthodox priest of the church in Derbent was among the dead. His wife said he had been shot in the head by one of the attackers.

The Kele-Numaz synagogue was severely damaged by fire, while police and security guards were killed outside, according to a statement from the Russian Jewish Congress (RJC).

Shortly after the attacks in Derbent, two gunmen ran into an Orthodox church in the city of Makhachkala, tried to set fire to its main icon and then opened fire.

A police post near the Makhachkala synagogue was also attacked.

Furthermore, in the nearby village of Sergokala, a police officer was injured a few hours later when a police car was attacked.

“This is a day of tragedy for Dagestan and the whole country” governor of Dagestan Sergei Melikov said in a video published on the Telegram messaging app.

Investigation still open

Although the assailants have not been officially identified, Russian law enforcement agencies told state-run news agency TASS on Sunday that the gunmen in Dagestan were “adherents of an international terrorist organization”.

Russian media also reported that among the gunmen were two sons of the head of the Sergokala district, Magomed Omarov, who was detained by police.

Melikov, told reporters Monday that Omarov has been relieved of his duties and expelled from the United Russia party, one of the main parties in the Russian parliament, pending an investigation.

Dagestan governor also said in a Telegram post early Monday that the active phase of the “operational and combat measures in Makhachkala and Derbent was completed but further investigations would continue”.