Ukrainian President Volodymyr Zelenskyy said on Friday that fighting in Donbas could lead to the biggest war in centuries.
Zelenskyy told the German newspaper that there would be intense fighting in the coming days.
It could be a big war like the world has not seen in hundreds of years, he said.
The Ukrainian president said they would defend their country until the end.
This chilling forecast is similar to what Dmytro Kuleba said to NATO members on Thursday.
Kuleba said that the battle for Donbas will remind you of the Second World War.
He used the warning to call for more heavy weaponry from the Western allies.
Russian President Vladimir Putin's forces are regrouping for a new eastern offensive after failing to capture Kyiv.
The train station in eastern Ukraine was packed with people who had fled their homes after a Russian rocket attack. More than 50 people were killed.
Kramatorsk is a town in the oblast that is home to pro-Russian forces. There is a region called the Donbas region.
From outside Mariupol in the south to the northern border, Luhansk and Donetsk are included.
Ukrainians have fought Russian-backed rebels in the region since the beginning of the year.
Nato Secretary-General Jens Stoltenberg said on Wednesday that they were expecting a major offensive in the near future.
A battle could last for weeks, but also months, and possibly for years, according to Stoltenberg.
US Defense Secretary Lloyd Austin said on Thursday that the US is giving intel to the Ukrainians.
Iryna Vereshchuk encourages Ukrainians living in the east to escape. If they don't flee, civilians will come under fire.