Five people were killed across Ukraine after Moscow launched more than 100 drones overnight, the latest in an almost nightly barrage the country has faced since the beginning of the war in 2022.

In a social media post marking the Chernobyl anniversary, Zelensky said Russia's invasion was "again bringing the world to the brink of a man-made disaster".

He highlighted how Russian drones regularly pass over Chernobyl and that one had hit its protective shell last year.

"The world must not allow this nuclear terrorism to continue, and the best way is to force Russia to stop its reckless attacks," he added.

The head of the International Atomic Energy Agency (IAEA), Rafael Grossi, and Moldovan President Maia Sandu joined the commemorative events.

Commenting on damage to the shell, which the environment group Greenpeace says raises the risk of a radioactive leak, Grossi said that "repairs should start as soon as possible and that leaving the situation as it is now is problematic."

Any repairs to the massive metal outer structure, which may potentially take up to four years, are virtually impossible due to Russia's invasion, according to Greenpeace.

- Worst nuclear accident -

Russia's nuclear agency Rosatom, the successor of the Soviet atomic energy ministry, which managed the facility, said: "To remember Chernobyl means to remember the people who bore the brunt of the disaster, and to take that experience into account in every decision we make today, to prevent a similar catastrophe."

Rosatom took over the plant in Ukraine's Zaporizhzhia, Europe's biggest civilian nuclear power complex, after it was occupied by Russia early in the invasion. The plant is now in shutdown mode. But Moscow and Kyiv repeatedly accuse each other of targeting the plant during the conflict, and Ukraine has called for sanctions against Rosatom.

Including Zaporizhzhia, Ukraine has four nuclear power plants, which are vital for the country's power supplies amid constant blackouts caused by relentless Russian attacks on energy infrastructure.

The 1986 explosion at Chernobyl was the worst civilian nuclear disaster in history and changed global perceptions of atomic energy.

Thousands are estimated to have died as a result of exposure to the radiation, though assessments of the precise human toll vary. Some 600,000 people involved in the clean-up operation -- known as "liquidators" -- were exposed to high levels of radiation.

Hundreds of thousands more were evacuated due to the radioactive contamination. The zone around the plant has become an exclusion zone, with abandoned towns, fields and forests.

In total, the disaster made large swathes of land in northern Ukraine and southern Belarus effectively uninhabitable.

- Overnight strikes -

Moscow and Kyiv exchanged drone barrages ahead of the anniversary events, causing civilian deaths in both countries.

Russian night-time strikes across Ukraine killed five people and wounded at least four others in the east, Ukrainian officials said.

In Russian-occupied Crimea and the Lugansk region, four people were killed in Ukrainian drone strikes, said local Moscow-backed authorities.

Meanwhile, the death toll from a 20-hour Russian barrage Saturday on Ukraine's central-eastern city of Dnipro rose to nine, authorities said.

Diplomatic efforts to end Europe's deadliest conflict since World War II are at a standstill with US mediation efforts diverted by the outbreak of the Middle East war in February.