Gunmen opened fire on places of worship in two cities of Russia’s southernmost Dagestan province on Sunday, killing at least 15 police officers and four civilians, including an Orthodox priest, in what appeared to be a coordinated attack.

Sergey Melikov, head of the Dagestan Republic, said at least six “militants” were also killed following the attacks on churches, synagogues and police posts in the cities of Derbent and the regional capital Makhachkala, which are about 120 kilometers (75 miles) apart.

The attacks took place in the republic of Dagestan in the North Caucasus, a predominantly Muslim region on the Caspian Sea that has a history of separatist and militant violence. The turbulence in the region has been further fanned by Russia’s war in Ukraine, where ethnic minorities have been disproportionately mobilized to fight.

Video and photos showed large flames and plumes of smoke billowing heavily out of a synagogue in Derbent, while footage filmed from the window of a building in Makhachkala shows black-clad unidentified people shooting at a police car in a street.

No group has yet claimed responsibility for the attacks, which come three months after ISIS affiliate ISIS-K said it carried out an assault at the Crocus City Hall in Moscow that claimed more than 140 lives in one of Russia’s deadliest terrorist atrocities in years.

Russian law enforcement agencies told state-run news agency TASS on Sunday that the gunmen in Dagestan were “adherents of an international terrorist organization.”

TASS reported Monday that five of the gunmen had been identified and that some of them were related to the leader of the Sergokalinsky district, which lies between Derbent and Makhachkala. It identified one of the men as former mixed martial arts fighter Gadzhimurad Kagirov. Kagirov had taken part in the attack on Derbent and was also a cousin of the head of the Sergokalinsky district, Magomed Omarov, it said. Omarov’s son and nephew were also among the attackers, authorities alleged.

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

Russia’s National Antiterrorist Committee (NAC) said Monday that “armed militants attacked two Orthodox churches, two synagogues and police officers” in the two cities. It added that the counter-terrorism operation in Makhachkala and Derbent had ended, TASS reported.

Four civilians were killed in the attacks, Russia’s investigative committee said on Monday, bringing the death toll up to 19.

Dagestan head Melikov 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.

Melikov described the possible involvement of “sleeper cells” and suggested the attacks may have had foreign help.

“Operative-search and investigative measures will be carried out until all participants of the sleeper cells are identified, which, undoubtedly, include some that were organized from abroad,” he added.

Three days of mourning have been declared in Dagestan following the deadly shootings, with state flags lowered to half-staff, Melikov said. Financial assistance will also be given to families of the victims, according to TASS.

Priest killed, synagogue set on fire

Dagestan is home to a small Christian minority and even smaller Jewish population that appeared to be among the targets of Sunday’s attacks.

A priest killed during an attack on a church in Derbent was identified as Father Nikolay by Dagestan Public Monitoring Commission Chairman Shamil Khadulaev.

The priest’s wife said her husband had been shot in the head by one of the attackers, contradicting earlier reports that his throat had been slit.

“He (the attacker) walked in, shot him in the head and left,” Valentina Kotelnikova said, according to a video published by the Russian online media outlet Mash on Monday.

Nighttime video, shared by the Republic of Dagestan’s Ministry of Internal Affairs, showed at least a dozen law enforcement officers — who appear to be armed and wearing tactical gear — outside the gates of a cathedral in northwest Makhachkala. CNN has geolocated the video to the gates of the Cathedral of the Assumption (Svyato-Uspenskiy Sobor), a Russian Orthodox cathedral in the city.

Earlier Sunday, TASS reported that a security guard was killed in a shootout at the cathedral, and 19 people had locked themselves inside the premises during the attack. Those who had holed up there have since been evacuated to safety, TASS reported, citing the Ministry of Internal Affairs of Dagestan.

Meanwhile, two synagogues in Dagestan — one in Derbent and one in Makhachkala — were also attacked, according to a statement from the Russian Jewish Congress (RJC).

Forty minutes before evening prayer, gunmen stormed the synagogue in Derbent and “set the building on fire using Molotov cocktails,” while police and security guards were killed outside, the RJC said.

Photos showed flames and plumes of smoke billowing out of a series of windows on at least one floor of the structure.

Dagestan’s small Jewish community is part of the Mountain Jews that historically lived for centuries in parts of Azerbaijan and what is now Russia’s Caucasus, according to Yad Vashem, the World Holocaust Remembrance Center in Israel.

The Israeli Foreign Ministry said the Derbent synagogue had “burned to the ground” and that local guards had been killed, while the synagogue in Makhachkala had been attacked by gunfire.

“As far as is known, there were no worshipers in the synagogues at the time of the attack, and there are no known casualties from the Jewish community,” the ministry said in a statement.

Security guards had been placed outside of local synagogues ever since an antisemitic mob stormed through the local airport in October in an attempt to block a passenger plane arriving from Tel Aviv.

The clashes left at least 10 people injured and videos showed a crowd of people inside the Makhachkala Uytash Airport and on the runway, some waving the Palestinian flag, others forcing their way through closed doors in the international terminal.

The airport attack came amid rising public anger in the region over Israel’s bombardment and blockade of Gaza in response to Hamas’ deadly October 7 attacks on Israel.

Investigation underway after police killed

An attack was also reported Sunday at a police traffic post in Makhachkala.

One of the law enforcement officers killed was Mavludin Khidirnabiev, the head of the “Dagestan Lights” police department, according to the Dagestan Ministry of Internal Affairs’ Telegram channel.

In an earlier Telegram post, Dagestan head Melikov said, “unknown persons made attempts to destabilize the social situation. Dagestan police officers stood in their way. According to preliminary information, there are victims among them.”

The identities of the attackers was being established, he said.

“The attacks, the encroachment on our brotherhood, on our multinational unity, on our confessional indivisibility, are an attempt to split our unity, thereby creating rifts between us,” Melikov said later in a video address.

The Investigative Directorate of the Investigative Committee of Russia for the Republic of Dagestan said it had launched a terror investigation into the attacks under the Criminal Code of the Russian Federation.

“All the circumstances of the incident and the persons involved in the terrorist attacks are being established, and their actions will be given a legal assessment,” the agency said in a statement.

While the investigation is underway, some local Russian officials pointed the finger at Ukraine, without providing evidence. The State Duma Deputy from Dagestan, Dmitry Gadzhiyev, said he believes “special services of Ukraine and NATO countries” could be behind the attack.

But Russian senator Dmitry Rogozin disputed the claim, saying in a Telegram post that writing off every terrorist attack as the “machinations of Ukraine and NATO” would lead to “big problems” for Russia.

A US State Department spokesperson said the US does not have an assessment of who was behind the attack, but called Russian claims that Ukraine and NATO were behind it “ridiculous.”

This is a developing story and will be updated.

Correction: This story has been updated to correct the timing of the attack in relation to evening prayers.