Russian forces shelled a nuclear research institute in Kharkiv, eastern Ukraine on Sunday damaging several buildings, though it is unclear whether any nuclear material was released at the facility as a result of the shelling, Ukraine's nuclear regulators said.

The attack took place two days after Russia attacked the Zaporizhzhya Nuclear Power Plant, Europe's largest nuclear power station in southern Ukraine, having already captured the Chernobyl nuclear power complex in the north.

The regulators said that a transformer facility at the Kharkov Institute of Physics and Technology was destroyed, and another facility containing nuclear fuel was damaged. It is unknown whether radiation levels around the institute have spiked and the authorities are looking into the damage.

The Ukrainian security authorities said that the attack on the institute could cause a large-scale environmental disaster.

The International Atomic Energy Agency's Director General Rafael Mariano Grossi expressed "grave concern" Sunday in a statement, saying that Russian forces control the Zaporizhzhya plant and that communication with operating staff at the power station has been cut off.