The UN's nuclear watchdog has raised grave concerns for military action near Ukraine's Zaporizhzhia nuclear power plant after it was hit by shelling, warning of "a very real risk" of nuclear disaster.
Both sides accused each other on Saturday of engaging in "nuclear terrorism".
Ukraine's state nuclear power company Energoatom said parts of the facility were "seriously damaged" by Russian military strikes, while Russia's defence ministry accused Ukrainian forces of shelling the plant.
"I'm extremely concerned by the shelling yesterday at Europe's largest nuclear power plant, which underlines the very real risk of a nuclear disaster that could threaten public health and the environment in Ukraine and beyond," said Rafael Mariano Grossi, director general of the International Atomic Energy Agency (IAEA).
"This is a serious and irresponsible breach of nuclear safety rules and another example of Russia's disregard for international norms."
Mr Grossi, who leads the United Nation's nuclear watchdog, urged all sides in the Ukraine conflict to exercise the "utmost restraint" around the plant.
Shells hit a high-voltage power line on Friday at the facility, prompting its operators to disconnect a reactor despite no radioactive leak being detected.
The plant was captured by Russian forces in early March in the opening stage of the war but it is still run by its Ukrainian technicians.
Energoatom said Russia wanted to disconnect the station from the Ukrainian electricity system and cause blackouts in the south of the country.
Moscow's forces, it said, had placed weapons and explosives in two of the power-generating units and mined the shoreline outside the plant.
"It is highly probable that all of this will cause a nuclear and radiation disaster," it said in a statement on Saturday.
Russia's defence ministry said damage to the plant had only been avoided thanks to the "skilful, competent and effective actions" of its units.
Mr Grossi said that military action jeopardising the safety and security of the Zaporizhzhia plant "is completely unacceptable and must be avoided at all costs".
Mykolaiv residents prepare for three-day curfew
Ukrainians queued for water in the southern frontline city of Mykolaiv on Friday before an unusually long curfew was set to begin, video posted on social media showed.
The region's governor said on Telegram the long curfew, from late Friday to Monday morning, aimed to catch people collaborating with Russia.
Mykolaiv, which has been shelled throughout Russia's invasion, lies close to Russian-occupied parts of the strategically important region of Kherson where Ukraine plans to conduct a counteroffensive.
Eyewitness video showed a crowd gathered to collect water that had been transported from Odesa by a group of volunteers.
Vitaliy Kim, governor of the Mykolaiv region, told residents the curfew running from 11pm Friday to 5am Monday did not mean the city was under threat or facing a looming attack.
US readies largest Ukraine weapons package
The Biden administration's next security assistance package for Ukraine is expected to be $US1 billion ($1.44 billion), one of the largest so far, and include munitions for long-range weapons and armoured medical transport vehicles, three sources briefed on the matter said on Friday.
The package is expected to be announced as early as Monday and would add to about $US8.8 billion in aid the United States has given Ukraine since Russia's invasion on February 24.
The officials, speaking on the condition of anonymity, said that President Joe Biden had not yet signed the next weapons package.
They cautioned that weapons packages can change in value and content before they are signed.
However, if signed in its current form, it would be valued at $US1 billion and include munitions for HIMARS, NASAMS surface-to-air missile system ammunition and as many as 50 M113 armoured medical transports.
The new package follows a recent Pentagon decision to allow Ukrainians to receive medical treatment at a US military hospital in Germany near Ramstein air base.
Last Monday, the Pentagon announced a separate security assistance package for Ukraine valued at up to $550 million, including additional ammunition for High Mobility Artillery Rocket Systems (HIMARS).
The White House declined to comment on the package.
The new package would be funded under the Presidential Drawdown Authority (PDA), in which the president can authorise the transfer of articles and services from US stocks without congressional approval in response to an emergency.
HIMARS play a key role in the artillery duel between Ukraine and Russia that has been described as "grinding" with very little movement of the front line in Ukraine's eastern Donbas region.
ABC/wires
