International alarm over the weekend shelling of Ukraine’s Zaporizhzhia nuclear complex grew on Monday, as Kyiv blamed Moscow for the attacks while seeking to address fears that their battle for control of the plant might trigger catastrophe.

United Nations chief Antonio Guterres, calling any attack on a nuclear plant a “suicidal thing”, demanded that U.N. nuclear inspectors be given access. The largest complex of its kind in Europe, Zaporizhzhia is situated in a southern region seized by Russian invaders in March and now targeted by Ukraine for a counter-offensive.

Kyiv appealed for the area to be demilitarised and for the International Atomic Energy Agency, the U.N.’s nuclear watchdog, to be let in.

Ukraine blamed Russia for weekend attacks in the area of the complex, which is still run by Ukrainian technicians. It said three radiation sensors were damaged, with two workers hospitalised with shrapnel injuries.

Petro Kotin, head of Ukraine’s state nuclear power company Energoatom, called for peacekeepers to be deployed in and run the Zaporizhzhia site, with operational control handed back to Ukraine.

He flagged the danger of shells hitting containers of highly radioactive spent nuclear fuel as especially dire. If two or more containers were broken, “it is impossible to assess the scale” of the resulting disaster.