Russian attacks against Ukraine’s damaged power grid have increased the probability of a catastrophic nuclear accident, according to US and European diplomats at an emergency meeting of the United Nations atomic watchdog.

At Khmelnitsky, a plant in western Ukraine with two existing reactors, connections are being built to a “shovel ready” area where four more reactors are planned, says Elias Gedeon of Westinghouse, an American partner on the project.

An armored vehicle belonging to the UN’s atomic watchdog was hit by a drone strike on its way to inspect a Ukrainian nuclear power plant on Tuesday, in an attack President Volodymyr Zelensky has blamed on Russia.