The United States blamed Moscow of using Ukraine's biggest nuclear power plant as a "nuclear shield" by deploying troops there, preventing Ukrainian forces from returning fire and risking a terrible nuclear accident.
Secretary of State Antony Blinken said the United States was "deeply concerned" that the Zaporizhzhia plant, which Russia was accused of firing shells dangerously close to in March, was now a Russian military base used to fire on nearby Ukrainian forces.
"Of course the Ukrainians cannot fire back lest there be a terrible accident involving the nuclear plant," Blinken told reporters after nuclear nonproliferation talks at the United Nations in New York on Monday.
Russia's actions went beyond using a "human shield" Blinken said, calling it a "nuclear shield."
At the New York talks, Ukraine's Deputy Foreign Affairs Minister Mykola Tochytskyi said "robust joint actions are needed to prevent nuclear disaster" and called for the international community to "close the sky" over Ukraine's nuclear power plants with air defense systems.
Russian President Vladimir Putin's Feb. 24 invasion of Ukraine has sparked the biggest conflict in Europe since World War II, killing thousands, displacing millions and leaving large parts of Ukraine in rubble.
The war has also caused a global food crisis, with Russia and Ukraine producing about a third of the world's wheat, while Western sanctions on Russia, a major energy provider to Europe, have caused a global energy crisis.
The first ship to carry Ukrainian grain through the Black Sea since Russia invaded five months ago left the port of Odessa for Lebanon on Monday under a safe passage deal.
The sailing was made possible after Turkey and the United Nations brokered a grain and fertilizer export agreement between Russia and Ukraine last month – a rare diplomatic breakthrough in a conflict that has become a drawn-out war of attrition.
The Sierra Leone-flagged ship Razoni will head to the port of Tripoli, Lebanon, after passing through Turkey's Bosporus Strait linking the Black Sea, which is dominated by Russia's navy, to the Mediterranean. It is carrying 26,527 tons of corn.
But there are still hurdles to overcome before millions of tons of Ukrainian grain can leave its Black Sea ports, including clearing sea mines and creating a framework for vessels to safely enter the conflict zone and pick up cargoes.
The United Nations has warned of the risk of multiple famines this year because of the war in Ukraine.
Known as Europe's breadbasket, Ukraine hopes to export 20 million tons of grain held in silos and 40 million tons from the harvest now under way, initially from Odessa and nearby Pivdennyi and Chornomorsk, to help clear the silos for the new crop.
Russia called the Razoni's departure "very positive" news, but it has denied responsibility for the food crisis, saying Western sanctions have slowed its exports and accusing Ukraine of laying underwater mines at entrance of its ports.
Russia and Ukraine accuse each other of laying the mines that now float around the Black Sea.
Signaling a deepening energy row between Russia and Europe, Russia on Monday said there was little it could do to help with urgent repairs to the Nord Stream 1 gas pipeline, its main gas pipeline to Europe, following further falls in Gazprom production and exports.
Gas from Russia met about 40% of European needs before Russia sent troops into Ukraine. Russia cut gas supplies via Nord Stream 1 to just 20% of capacity last week, saying a turbine sent to Canada for maintenance had not been returned and other equipment needed repair.
Russia invaded Ukraine in what it called a "special operation" to demilitarize its neighbor. Ukraine and Western nations have dismissed this as a baseless pretext for war.
After failing to capture the capital Kyiv early in the war, Russia now aims to capture the eastern Donbass region, made up of Donetsk and Luhansk, partially occupied by Russia-backed separatists before the invasion, and capture more of the south, having already annexed Crimea from Ukraine in 2014.
Ukrainian presidential adviser Oleksiy Arestovych told the media about 22,000 Russian troops were preparing to advance on the cities of Kriviy Rih and Mykolaiv, where a "sufficiently large" Ukrainian force lay in wait.
In the Kherson region, which is mostly under Russian control, Ukrainian troops had liberated some 50 towns, said Yuri Sobolevsky, deputy head of the ousted Kherson regional council.
"Russian troop in Kherson region are sustaining considerable losses," Sobolevsky wrote on Telegram.
Reuters was unable to verify the battlefield report.
Serhiy Gaidai, governor of Luhansk region, which is nearly all under Russian control, said foreign fighters were arriving to help Russian forces.
"We have noticed that more and more private military companies coming into the area – the Wagner Group," Gaidai told Ukrainian TV, adding that these irregular forces were motivated by "money and looting."
Russian private military firm Wagner has likely been given responsibility for sectors of the front line in eastern Ukraine, possibly as Russia is facing a shortage of infantry, Britain's Ministry of Defense said last week.
Gaidai said partisans were destroying infrastructure, including gas and water networks, in battered Luhansk towns to slow Russian forces.
