Death toll rises to 20 in Russia's Dagestan attack, 3-day mourning declared

The death toll in the attacks by gunmen on synagogue and church in Russia's Dagestan has risen to 20, Al Jazeera reported, citing Russia's Investigative Committee.

Following this, three days of mourning has also been declared in Russia's North Caucasus region of Dagestan.

At least 15 police officers died alongside several civilians, including an Orthodox priest. Five attackers were also reported to have been "liquidated". At least 12 people were also injured in the attacks.

The Russian Orthodox Church said its archpriest Nikolai Kotelnikov was also "brutally killed" in Derbent.

The gunmen attacked church, synagogue, and police post in the cities of Derbent and Makhachkala on Sunday, the festival of Pentecost for the Russian Orthodox Church. The places were also reportedly attacked.

Videos posted on social media and shown on Russian TV showed the skies of Derbent, which is home to an ancient Jewish community in the mainly Muslim region, filled with smoke and flames after the synagogue was set on fire, as reported by Al Jazeera.

The Investigative Committee said it had opened criminal investigations over "acts of terror" in Dagestan, which neighbours Chechnya and is one of the poorest areas of Russia in the country.

Dagestan's authorities announced on Monday the start of three days of mourning.

Flags will be flown at half-mast throughout the republic, RIA reported, while cultural institutions and television and radio companies have cancelled all entertainment and entertainment events and programmes.

The Russian news agency TASS, reported citing law enforcement agencies, that the gunmen were members of "an international terrorist organisation". However, the attackers have not yet been identified.

Notably, the attacks come three months after some 133 people were killed when gunmen opened fire at a rock concert in the Crocus City Hall on the outskirts of Moscow. Islamic State in Khorasan Province (ISKP), based in Afghanistan, said it was behind that attack, although Moscow claimed without evidence that Ukraine had a role.

Russia's FSB security service in April said it had arrested four people in Dagestan on suspicion of involvement in plotting the Crocus City Hall attack, Al Jazeera reported.