Kyiv | Ukraine's nuclear energy agency says it has put the last operating reactor at Europe's largest nuclear power plant into a “cold shutdown” — a safety precaution amid catastrophic flooding from the collapse of a nearby dam as Russia's war on Ukraine drags on through its 16th month.

Russian forces continued pummeling the country with missiles and drones overnight, with Ukrainian officials reporting at least four deaths and damage to a military airfield.

Five out of six reactors at the Zaporizhzhia Nuclear Power Plant, which is occupied by Russian forces, are already in a state of cold shutdown, in which all control rods are inserted into the reactor core to stop the nuclear fission reaction and generation of heat and pressure.

Energoatom, the Ukrainian nuclear agency, said in a statement late Friday that there was “no direct threat” to the Zaporizhzhia plant due to the breach of the Kakhovka dam further down the Dnieper River, which has forced thousands of people to flee flooding and also sharply reduced water levels in a reservoir used to help cool the facility.

The last reactor was put into cold shutdown on Thursday, Energoatom said, adding that other factors in the decision included shelling near the site which has damaged overhead lines connecting the plant to Ukraine's energy system.

With all nuclear reactions stopped, temperatures and pressure inside reactors gradually decline, reducing the required intensity of water cooling of the radioactive fuel. This is a nuclear power plant's safest operating mode. Energoatom employees are still working at the power plant, although it remains controlled by the Russians.

The site's power units have not been operating since September last year. The head of the International Atomic Energy Agency is due to visit Ukraine in the coming days.

Analysts and Russia say that Ukraine has launched a counteroffensive in southern Ukraine, potentially aiming to retake territory near the plant.

Also on Saturday morning, Ukrainian authorities reported that at least four civilians have died across the country as Russian forces launched Iranian-made Shahed drones, missiles, and artillery and mortar strikes. Ukraine's State Emergency Service reported that three people were killed and over two dozen wounded overnight in an attack targeting the Black Sea port of Odesa. A spokesperson for Ukraine's southern operational command, Natalia Humeniuk, said that two children and a pregnant woman were among those wounded.

In Ukraine's northeast, a 29-year-old man was killed as more than 10 drones targeted the Kharkiv region, its governor, Oleh Syniehubov, reported Saturday. He added that at least three other civilians were wounded.

In the Poltava region further west, there was damage to a military airfield struck overnight during a Russian drone and missile attack, local Gov. Dmytro Lunin reported. Lunin said no one was hurt. As of Saturday morning, there was no additional comment from the Ukrainian army or officials on the extent of the damage.

The Ukrainian air force said that during the night, it had shot down 20 out of 35 Shahed drones and two out of eight missiles “of various types” launched by Russian forces.