The United States' top diplomat and defence chief were Sunday set to make their first wartime visits to Kyiv since Russia invaded Ukraine two months ago, with fierce battles raging in the east of the country.
The trip by Secretary of State Antony Blinken and Defense Secretary Lloyd Austin comes as the war enters its third month with thousands dead and millions displaced.
A series of European leaders have already travelled to Kyiv to meet President Volodymyr Zelensky and underscore their support, but the United States -- a leading donor of finance and weaponry -- has yet to send any top officials.
In his daily video address Saturday night, Zelensky said he was preparing for "tomorrow's important talks with American partners". The State Department declined to comment on the highly sensitive trip by two of President Joe Biden's top cabinet members.
Their visit comes as Russian forces show no sign of easing their attacks and after a missile strike on the southern city of Odessa that Ukraine said killed eight people, including an infant.
"Among those killed was a three-month-old baby girl. How did she threaten Russia? It seems that killing children is just a new national idea of the Russian Federation," Zelensky said.
He also accused Russia of being a terrorist state and of acting like Nazis in the shattered port city of Mariupol, which has been devastated by weeks of intense bombardment.
"New facts about the crimes of the occupiers against our Mariupol residents are being revealed. New graves of people killed by the occupiers are being found. We are talking about tens of thousands of dead Mariupol residents," he said.
The latest of many attempts to evacuate civilians from Mariupol failed Saturday, and an embattled unit of Ukrainian fighters holed up in tunnels under a sprawling steel mill there appeared in increasingly desperate straits.
Zelensky also issued a new call Saturday for a meeting with his Russian counterpart Vladimir Putin "to end the war."
"I think that whoever started this war will be able to end it," Zelensky said, adding he was "not afraid" to meet the Russian leader, who attended an Orthodox Easter service in Moscow.
But he again stressed that Kyiv would abandon talks with Moscow if its troops in Mariupol were killed.
Zelensky also criticised a decision by UN Secretary General Antonio Guterres to visit Moscow on Tuesday, before heading to Kyiv.
"There is no justice and no logic in this order," he said.
"The war is in Ukraine, there are no bodies in the streets of Moscow. It would be logical to go first to Ukraine, to see the people there, the consequences of the occupation," he said.
Around 200 residents gathered at a designated evacuation point in Mariupol on Saturday but were "dispersed" by Russian forces, city official Petro Andryushchenko said on Telegram, adding: "The evacuation was thwarted."
He claimed others had been told to board buses headed to places controlled by Russia.
Mariupol, which the Kremlin claims to have "liberated", is pivotal to Russia's war plans to forge a land bridge to Russian-occupied Crimea -- and possibly beyond, as far as Moldova.
In its latest analysis, the US-based Institute for the Study of War said Russian forces did not appear to be pausing to refit or mass their troops as they redeployed and were likely to step up their offensives.
"Russian forces will likely increase the scale of ground offensive operations in the coming days, but it is too soon to tell how fast they will do so or how large those offensives will be," it said.
Ukraine says hundreds of its forces and civilians are holed up inside the Mariupol steel plant. Kyiv has repeatedly called for a ceasefire to allow civilians -- many barely surviving with little or no access to food or water -- to exit safely.
But on Saturday a Ukrainian presidential adviser, Oleksiy Arestovich, said Russian forces had resumed air strikes on the factory.
"Our defenders hold on regardless of the very difficult situation and even carry out counter-raids," he said.
Further west, a missile struck a residential building in the Black Sea port of Odessa, killing eight people and wounding at least 18, according to Zelensky, who said five missiles hit the historic city.
"We will identify all those responsible for this strike; those responsible for Russia's missile terror," he said.
Russia's defence ministry said it had targeted a major depot stocking foreign weapons near Odessa, attacks that upended the relative calm the city has enjoyed since the beginning of the war.
The ministry also charged that Ukrainian special services in Odessa were preparing a "provocation with the use of toxic chemical substances" that could then be blamed on Russia.
Western powers have accused Russia in the past of making such accusations as a cover or diversion for attacks its own forces are planning.
The latest fighting came a day after a senior Russian military officer said they aimed to take full control over the eastern Donbas region and southern Ukraine.
Russian forces, which withdrew from around Kyiv and the north of Ukraine after being frustrated in their attempts to take the capital, already occupy much of the Donbas and the south.
After changing their strategic focus to southern and eastern Ukraine, Russian forces left behind a trail of destruction around Kyiv, including in the commuter town of Bucha.
A United Nations mission to Bucha documented "the unlawful killing, including by summary execution, of some 50 civilians there", the UN's Office of the High Commissioner for Human Rights said.
Russian forces had "indiscriminately shelled and bombed populated areas, killing civilians and wrecking hospitals, schools and other civilian infrastructure, actions that may amount to war crimes".
Tania Boikiv, 52, said Russian troops took her husband from their home in Bucha, held him for two weeks, then beat him to death as they retreated.
"The most terrible thing in my life is that my husband, my loved one, is gone," she told AFP. "I don't know what could be worse."