A coordinated terror attack in two cities in Dagestan, a Muslim majority republic in Russia’s North Caucasus, appears to be ongoing, state owned news agency TASS reported on Sunday evening.

Unknown attackers in the cities of Derbent and Makhachkala attacked two Orthodox churches, a synagogue and a traffic police post, TASS reported citing the National Anti-Terrorist Committee.

The Interior Ministry told state-owned news agency RIA Novosti that six policemen had been killed and that 12 others had been wounded, while a 66-year-old bishop was reportedly killed in an attack on a church in Derbent.

The security forces reported the killing of two militants who attacked the church and synagogue in Derbent. Two more alleged shooters were reportedly identified among holidaymakers on the city’s beach and were detained.

The Investigative Committee of Russia said it had opened a criminal investigation into the attack and that its staff in Dagestan were at the scene of the incident in Derbent.

A counter-terrorist operation has been initiated, with all routes in and out of Derbent and Makhachkala blocked and police inspecting vehicles, according to eye-witness accounts on social networks.

The attackers may be related to international terrorist organisations, according to a source inside Dagestan’s law enforcement agencies quoted by Russian media outlet RBC: “Judging by the actions of the attackers, their shouts and appearance, the terrorists belong to an Islamist terrorist organisation.”

Meanwhile, another shooting reportedly took place on Sunday on Russia’s border with Abkhazia, a breakaway region that is occupied by Russian forces despite being legally part of Georgia. The shooting, in which one person was killed and three others were wounded, took place near a checkpoint on the Psou River, TASS reported citing the local prosecutor’s office.