A rural police station in southern Russia has come under attack in what is suspected to be a suicide bombing, reports said Monday.

Three men attacked a police station in Russia’s Stavropol region in the north Caucasus on Monday including at least one suicide bomber, the Interior Ministry said.

The police said they had been put on a high state of alert in the wake of the attack.

Local authorities said that five explosions were heard in all.

The attack took place close to the volatile majority-Muslim North Caucasus area, where ultra-radical jihadists intent upon carving out a breakaway caliphate have targeted policemen in a series of car bombings and shootings.

“An attack took place on a regional police station,” Reuters cited a spokesman for the Interior Ministry in Stavropol as saying. “One of the attackers blew himself up, two others were killed.”

Initial reports said no police officers or locals were hurt in the blasts, citing a regional branch of Russia’s Interior Ministry.

Accounts of what happened varied. Some Russian news agencies cited unnamed police sources as saying three suicide bombers had managed to blow themselves up and that there were four attackers in total.

The interior ministry spokesman said the authorities had responded to the attack by activating the “Fortress Plan,” which meant police had been put on a higher state of military-style readiness.

An eyewitness video on the lifenews.ru news portal filmed at what it said was the scene of the attack showed and assorted debris in front of it as a continuous alarm sounded in the background.

Video purporting to be from the scene was posted to social media by the Russian outlet Life News. It showed the blackened entrance to the police station and debris outside the front entrance, as well as damage to cars and buildings in the street outside apparently as a result of the blasts.

The man filming the video, who was not named, said there had been five explosions and automatic gun fire.