Gunmen attacked churches and synagogues in Russia's North Caucasus region of Dagestan on Sunday, killing at least 15 police officers, a priest and a security guard, officials said.
The assailants launched simultaneous attacks in Makhachkala, the region's largest city, and in Derbent.
The attacks coincided with the Christian Orthodox festival of Pentecost, which was widely celebrated across Russia on Sunday.
Russia's Investigative Committee said it had opened an investigation into the “acts of terror” in Dagestan, which has previously been the scene of extremist attacks.
“This evening, in Derbent and Makhachkala, unknown [attackers] made attempts to destabilise the situation in society,” Dagestan's leader Sergei Melikov wrote on Telegram, without naming any culprits.
Mr Melikov said more than 15 police officers “fell victim” to what he described as a “terrorist attack". Russian officials said police killed four gunmen in Makhachkala and two in Derbent.
The assailants attacked “two Orthodox churches, a synagogue and a police checkpoint”, the National Anti-terrorism Committee told Russian media.
Patriarch Kirill, the head of the Russian Orthodox Church and a staunch supporter of the Kremlin, said the “enemy” was looking to destroy “interreligious peace” in the country.
The church said arch-priest Nikolai Kotelnikov was “brutally killed” in Derbent.
Gunmen also attacked synagogues in the cities but no casualties were reported. The Kele-Numaz synagogue in Derbent, which is home to an ancient Jewish community, was set ablaze.
Mr Melikov said June 24 to 26 had been declared days of mourning in the region.
Pictures of the dead policemen were lined up on the street beside red carnations in Dagestan.
"This is a day of tragedy for Dagestan and the whole country," he said.
Role of ISIS
The attack comes three months after ISIS gunmen carried out a major terrorist attack in Moscow.
In March, four heavily armed gunmen killed 145 people and injured more than 500 others in an attack Moscow's Crocus City Hall.
The city hall attack was claimed by ISIS-Khorasan, the branch of the global terrorist group based in Afghanistan and central Asia. The four men accused of carrying out the attack were all citizens of Tajikistan believed to be affiliated with ISIS.
The following month, Russia's FSB security service said four people in Dagestan were arrested on suspicion of plotting the deadly attack.
ISIS-K praised Sunday's attack in Dagestan but did not claim responsibility for it.
In a statement, the group said it was carried out by "brothers in the Caucasus who showed they are still strong".
According to the Washington-based Institute for the Study of War, the attack was likely carried out by ISIS branch in the North Caucasus, which is called Vilayat Kavkaz.
The institute described the attack as "complex and co-ordinated".
Mr Melikov blamed members of Islamic “sleeper cells” directed from abroad. He said in a video statement that the assailants aimed at “sowing panic and fear” and attempted to link the attack to Moscow’s military action in Ukraine, but provided no evidence for that claim.
Russian news reports said the attackers included the two sons and a nephew of Magomed Omarov, the head of the main Kremlin's party United Russia's regional branch in Dagestan. Mr Omarov was detained by police for interrogation and United Russia quickly dismissed him from its ranks.
In the early 2000s, Dagestan saw near-daily attacks on police and other authorities that were blamed on extremists. After the emergence of ISIS in Syria and Iraq in 2015, many militants from Dagestan travelled to the region to join its ranks.
Dagestan lies east of Chechnya, in the mountainous and multi-ethnic Caucasus region.
The Russian empire expanded into the Caucasus in the late 18th and early 19th centuries, but an insurgency after the 1991 fall of the Soviet Union led to two wars between the Russian state and separatists.
In August 1999, Chechen fighter Shamil Basayev led fighters into Dagestan in a bid to aid Dagestani Wahhabist fundamentalists, triggering a major bombing campaign by the Russian military ahead of the Second Chechen War.
- With reporting from agencies
