The authorities of the Zaporozhye region located in Southeastern Ukraine said Monday they were going ahead with their plans of holding a referendum on joining Russia.

"I signed a decree... to start working on the issue of organizing a referendum on the reunification of the Zaporozhye region with the Russian Federation," Yevgeny Balitsky, the head of the region's administration said on social media.

He indicated earlier that the referendum could be held in the autumn. Balitsky had signed in July a decree announcing the start of preparations for a referendum on joining Russia and the creation of an election commission to conduct elections.

Ukrainian troops fired at the territory of the Zaporozhye nuclear power plant (NPP) on Friday, where a fire broke out immediately. 

As a consequence, two vital power lines that are necessary for energy providing were cut off, leaving more than 10,000 inhabitants of the Zaporozhye region without power and water.

"Under the international convention adopted by the resolution of the UN General Assembly of April 13, 2005, we consider these criminal actions of the Ukrainian authorities to be an act of nuclear terrorism," the head of the Russian National Defense Control Center, Colonel General Mikhail Mizintsev, told a press briefing.

According to the official, the shelling ignited a large fire in the vicinity of the plant, which is being controlled by personnel from a local fire department.

"At the moment, it is not possible to proceed with the localization of the fire as severed power lines are under voltage, and there is a high probability of precipitation," he said.

The official said that if an accident were to happen, which the shelling could potentially cause, the effects would surpass the scale of Chernobyl and Fukushima - the entire territories of Ukraine, Donetsk, Lugansk, Russia, Belarus, Moldova, Bulgaria and Romania would be contaminated by nuclear waste.

He urged the United Nations, the International Atomic Energy Agency, and other organizations to condemn the Ukraine military for its actions and to take immediate measures to prevent further aggression against Ukraine's nuclear facilities.