Ukraine's President Volodymyr Zelenskyy said in the early hours of Saturday that Russian troops would attempt to take the capital city Kyiv during the night.
In a video address to the nation, he said: "I have to say absolutely openly. This night will be more difficult than the day. Many cities of our state are under attack.
"Special attention on Kyiv -- we cannot lose the capital," he added in the clip released by the presidency.
"I am turning to our defenders, male and female, on all fronts: this night the enemy will use all the forces it has to crush our defence in a treacherous, harsh and inhumane way.
"Tonight they will attempt a storming," he added, in an apparent reference to the capital Kyiv.
President Zelenskyy said that on Friday he spoke to many Western leaders, including French President Emmanuel Macron, German Chancellor Olaf Scholz, and US President Joe Biden.
"We have agreed on more aid, more support, significant support for our state," he said.
"Our main aim is to end this carnage."
Western capitals have imposed sweeping sanctions on Moscow and personal sanctions on President Vladimir Putin in response to the Kremlin's invasion of Ukraine that has claimed dozens of lives and displaced tens of thousands of people.
