A huge explosion has rocked the Rostov-on-Don region in southern Russia as locals report seeing a large flash of light.

Residents near the city lost power in their homes after explosion. Videos of the flash have been shared online.

According to reports, the explosion occurred at an electricity substation.

The office of the Mayor of Rostov said that the explosion and power outage may have originated at a water treatment facility called JSC Rostovvodokanal, a company that designs water supply systems.

The statement suggests a problem with the pumping equipment.

READ MORE: Russian prisoners take guards hostage as special forces storm prison with guns

Locals were left without a water supply for a number of hours. This comes during a chaotic 24-hour period for the city of Rostov.

On Sunday, Russian special forces killed six men linked to ISIS after they took two prison guards hostage.

There is no evidence to suggest the explosion was linked to the ISIS attack.

Russian state media reports that the men in question have already been convicted of terrorism offences.

According to reports, the 6 attackers knocked out window bars and climbed down several floors by rope before snatching the guards.

The guards were armed with axes and knives. Russian forces located the men before taking them out. Footage showed audible gunshots from inside the prison.

Russia‘s federal penitentiary service said in a statement: “The criminals were eliminated. The employees who were being held hostage were released. They are uninjured.”

The attack comes after members of ISIS-K attacked Crocus City Hall in Moscow back in March.

Four gunmen carried out a mass shooting and slashing attack on the people gathered for a rock concert. They then set the venue on fire.

Investigators said 145 people had been killed.

ISIS seems to be ramping up its attacks on Russia. Moscow played a key role in striking ISIS during the war in Syria as Vladimir Putin sought to prop up his ally in the country, dictator Bashas al-Assad.

Russian media reports that the hostage-takers in Rostov were from Russia’s southern republic of Ingushetia.