Ukraine's nuclear watchdog says Russian forces have shelled a nuclear research installation in the city of Kharkiv.

The regulator said on Sunday that the installation is located in the compounds of Kharkiv Institute of Physics and Technology. The installation handles nuclear material.

The regulator said the full extent of damage remains unknown. But it adds the surface of the installation's main building was damaged "in some places" with a substation "completely destroyed."

The regulator said, "The Russian Federation has committed another act of the nuclear terrorism!!!"

Last week, Russian forces attacked and seized the Zaporizhzhia Nuclear Power Plant in southeastern Ukraine.

Ukraine's interior ministry warns that an attack on a nuclear facility could cause extensive damage.

The institute's website says it is one of Ukraine's largest physics research facilities. It adds the institute was established in 1928, and has been involved in nuclear and other research since the collapse of the Soviet Union.

The Japan-based Technical Secretariat on Cooperation for the Elimination of Nuclear Weapons Reduced in the Former Soviet Union says the Kharkiv institute has kept nuclear materials since the Soviet era.