Gunmen have opened fire on a synagogue and two Orthodox churches in Russia's Dagestan region in a suspected terror attack.

At least six police officers and a priest have been killed in Derbent and Makhachkala. The priest, 66-year-old Father Nikolay, had his throat cut.

Video circulating on social media shows the gunmen exchanging fire with police and roads out of Makhachkala closed.

The synagogue in Derbent - the southernmost city in Russia located on the Caspian Sea - was set on fire, officals said.

Makhachkala, the capital of Dagestan, is located about 75 miles north along the coast.

In a statement, Russia's interior ministry said six police officers had been killed and a further 12 are injured.

Russia's Investigative Committee said the attacks are being considered "acts of terror."

In a post on Russian social media platform VK, the Muftiate of the Republic of Dagestan said: "Law enforcement officers, clergy, and ordinary citizens became victims of monstrous terrorist attacks."

In Makhachkala, a police checkpoint was targeted and images in Russian media show a police vehicle on fire.

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A priest was killed in a church in Derbent, Shamil Khaduleav, the Dagestan Public Monitoring Commission Chairman, said.

Officials told Russian state-owned news agency RIA Novosti two “militants” have been killed.

Khadulaev said Father Nikolay was killed in the church in Derbent and his throat was cut.

“According to the information I received, Father Nikolay was killed in the church in Derbent, they slit his throat. He was 66-years-old and very ill,” he said.

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