MOSCOW: Gunmen on Sunday attacked a synagogue and churches, killing a priest and six police officers in Russia's Caucasus region of Dagestan, the national counter-terrorism agency and police said.

The attacks took place in Dagestan's largest city of Makhachkala and in the coastal city of Derbent.

Russia's Investigative Committee said it had opened criminal probes over "acts of terror".

Dagestan is a largely Muslim region of Russia bordering Georgia and Azerbaijan.

"This evening in the cities of Derbent and Makhachkala armed attacks were carried out on two Orthodox churches, a synagogue and a police check-point," said the National Antiterrorism Committee in a statement to RIA Novosti news agency.

"As a result of the terrorist attacks, according to preliminary information, a priest from the Russian Orthodox Church and police officers were killed."

In all, six police officers had been killed and another 12 wounded in the attacks, the spokesperson for Dagestan's interior ministry, Gayana Gariyeva, told RIA Novosti.

A 66-year-old priest was killed in Derbent, the press secretary of Dagestan's interior ministry, Gariyeva told the agency.

"The synagogue in Derbent is on fire," the chairman of the public council of Russia's Federation of Jewish Communities, Boruch Gorin wrote on Telegram.

"It has not been possible to extinguish the fire. Two are killed: a policeman and a security guard".

He added: "The synagogue in Makhachkala has also been set on fire and burnt down. During the attack on the Orthodox church in Derbent, the priest's throat was cut."

The leader of Dagestan, Sergei Melikov, wrote on Telegram: "This evening in Derbent and Makhachkala unknown (attackers) made attempts to destabilise the situation in society.

"They were confronted by Dagestani police officers."