Ukraine's defence minister has said Russia is preparing a major new offensive, and warned that it could begin as soon as 24 February, APA reports citing BBC.
Oleksii Reznikov said Moscow had amassed thousands of troops and could "try something" to mark the anniversary of the initial invasion last year.
The attack would also mark Russia's Defender of the Fatherland Day on 23 February, which celebrates the army.
Meanwhile, three people have died in an attack on the city of Kramatorsk.
Seven others were wounded in the city in Donetsk region after a Russian missile struck a residential building, the provincial governor said.
The toll is expected to rise as rescuers comb through the wreckage.
"The only way to stop Russian terrorism is to defeat it," Mr Zelensky wrote on social media about the attack. "By tanks. Fighter jets. Long-range missiles."
Ukraine has recently renewed calls for fighter jets to help protect itself from air attacks after Germany, the US and the UK agreed to send them tanks.