In his first visit to Ukraine since Russia launched a full-scale invasion on February 24, António Guterres visited several towns and villages outside kyiv where Russian forces are accused of killing civilians.

“I imagine my family in one of these now destroyed and black houses. I see my granddaughters fleeing in panic,” the UN chief said in Borodianka, a ruined town northeast of the Ukrainian capital.

“War is nonsense in the 21st century. War is diabolical,” he added.

In the nearby town of Bucha, where dozens of plainclothes bodies, some with their hands tied behind their backs, were discovered this month after a Russian withdrawal, António Guterres backed an International Criminal Court investigation into possible war crimes in Ukraine.

“I call on the Russian Federation to accept, to cooperate with the ICC,” he implored the Kremlin.

The UN chief will meet Ukrainian President Volodymyr Zelensky later.

On Tuesday, he met Russian President Vladimir Putin in Moscow, reiterating calls for Moscow and Kyiv to work together to establish “safe and efficient” humanitarian corridors in war-torn Ukraine.

A UN representative in Ukraine said on Thursday she was preparing for a “hopeful” evacuation from the beleaguered port city in southeastern Ukraine, where kyiv says injured civilians and fighters are trapped.

“The UN is fully mobilized to help save Ukrainian lives and help those in need,” UN Resident Coordinator and Humanitarian Coordinator in Ukraine Osnat Lubrani wrote on Twitter.

“Difficult weeks”

With the war now in its third month and claiming thousands of lives, kyiv admitted Russian forces were advancing east, capturing a series of villages in the Donbass region.

The first phase of the Russian invasion failed to reach kyiv or overthrow Zelensky’s government after encountering strong Ukrainian resistance reinforced by Western weapons.

The campaign has since refocused on seizing the east and south of the country while increasingly using long-range missiles against western and central Ukraine.

Ukrainian Defense Minister Oleksiy Reznikov acknowledged that the country faced “extremely difficult weeks” as Moscow tried “to inflict as much suffering as possible”.

The Russian Defense Ministry said on Thursday that its forces had destroyed two arms and ammunition depots in eastern and southern Ukraine with “high-precision missiles”.

Its air force targeted 67 Ukrainian military sites while air defense systems destroyed a Ukrainian fighter jet in the Luhansk region, the ministry added.

Russia has also targeted weapons supplied by the West in recent days, as the United States and Europe increasingly heed Zelensky’s call for heavier firepower.

In a defiant speech on Wednesday, Putin said that if Western forces intervened in Ukraine and created “unacceptable threats”, they would face a “lightning-fast” military response.

“threatening security”

“We have all the tools for this, which no one else can boast of having,” he told politicians, implicitly referring to ballistic missiles and Moscow’s nuclear arsenal.

The Kremlin reiterated the warnings on Thursday, calling Western arms shipments dangerous for European security.

“The tendency to pump weapons, including heavy weapons to Ukraine – these are actions that threaten the security of the continent, cause instability,” spokesman Dmitry Peskov told reporters.

Western allies still fear being drawn into war with Russia, but have stepped up military support as Ukraine has maintained its fierce resistance.

US President Joe Biden is due to deliver a speech on Thursday on “support for Ukrainians defending their country and their freedom against Russia’s brutal war,” the White House said.

On Wednesday evening in London, British Foreign Secretary Liz Truss launched a new appeal for arms deliveries to Ukraine, including heavy weapons, tanks and planes, while demanding that “all ‘Ukraine’ be released.

Responding to Putin’s latest threats to kyiv’s Western allies, British Defense Secretary Ben Wallace claimed he was “rolling the field” for a major announcement to mark the nation’s “Victory Day” celebration. World War II in Russia on May 9.

In its economic standoff with the West, Russia on Wednesday cut gas supplies to Bulgaria and Poland, members of the EU and NATO.

‘Blackmail’

Brussels has warned that it will not waver in its support for Kyiv, accusing the Kremlin of attempting “blackmail”.

Bulgaria and Poland now receive gas from EU neighbours, as European Commission President Ursula von der Leyen pledged an “immediate, united and coordinated” response.

As the 27-member bloc, which relied on gas from Russia, worked to diversify its energy sources, she said: “The era of Russian fossil fuels in Europe will come to an end.”

European powers have imposed massive sanctions on Russia since Putin’s invasion, while shipping arms to Ukraine’s defenders.

But they have made slow progress to hit Moscow’s vast exports, with many EU members – notably the German industrial giant – dependent on Russian energy.

Putin stepped up the pressure by insisting on paying for gas in rubles – hoping to force his enemies to back his currency.

Tensions have also risen in Transnistria, a breakaway region of Moldova that borders southwestern Ukraine.

Pro-Russian separatists in the region said shots were fired across the border on Wednesday towards a village housing a Russian arms depot after drones flew over Ukraine.

The unrecognized region has reported a series of explosions in recent days that it has called “terrorist attacks”, leading kyiv to accuse Moscow of seeking to spread the war further into Europe.

“We are alarmed by the escalation of tensions in Transnistria,” Russian Foreign Ministry spokeswoman Maria Zakharova said, saying Moscow expected “a thorough and objective investigation.”