Russian forces seized the Zaporizhzhia nuclear power plant (ZNPP) in southern Ukraine in the first days of its 2022 invasion.

Both sides regularly accuse each other of endangering safety at the site, Europe's largest nuclear facility.

"For 785 days now, Russian terrorists have held the Zaporizhzhia NPP hostage," Zelensky said on social media.

"It is the entire world's responsibility to put pressure on Russia to ensure that ZNPP is liberated and returned to full Ukrainian control, as well as that all Ukrainian nuclear facilities are protected from Russian strikes," he added.

"This is the only way to prevent new radiation disasters, which the Russian occupiers' presence at ZNPP constantly threatens."

The call came 38 years after the meltdown of the Chernobyl nuclear power plant in northern Ukraine, then part of the Soviet Union.

The incident, which is considered the world's worst nuclear disaster, contaminated vast areas of Ukraine, Belarus and Russia. Swathes of western Europe were also exposed to radiation.

"The Chernobyl disaster demonstrated how rapidly deadly threats can emerge," Zelensky said on Friday.

Russian forces captured the decommissioned Chernobyl facility on February 24, 2022 -- the first day of its invasion, when it sent troops into Ukraine from Belarus -- but abandoned it weeks later.

Russian troops have controlled the Zaporizhzhia plant since early March 2022.

The International Atomic Energy Agency, which has dispatched inspectors to the Zaporizhzhia nuclear power plant, has expressed concern over safety at the plant.

Moscow has accused Ukraine of firing drones at the power station, while Kyiv says Moscow has militarised the facility and is holding it "hostage".