Russia is planning a major offensive to coincide with the one-year anniversary of the war in Ukraine on 24 February, according to the country’s defence minister, Oleksii Reznikov.

Speaking to French media, Reznikov warned that Russia would call on a large contingent of mobilised troops. Referring to Russia’s general mobilisation of 300,000 conscripted soldiers in September last year, he claimed that numbers at the border suggest the true size could be closer to 500,000.

“We do not underestimate our enemy,” Reznikov said. “Officially, they announced 300,000, but when we see the troops at the borders, according to our assessments it is much more.”

The Guardian was unable to independently verify these figures.

On Wednesday evening, President Volodymyr Zelenskiy said Russian forces were trying to make gains that they could show on the February anniversary of their invasion, and issued a dire account of the situation in the eastern province of Donetsk.

“A definite increase has been noted in the offensive operations of the occupiers on the front in the east of our country. The situation has become tougher,” Zelenskiy said in a video address.

Reznikov said the offensive would probably be concentrated in two areas: the country’s east, which has seen heavy fighting over recent weeks; and the south.

“We think that, given that [Russia] lives in symbolism, they will try to try something around February 24.”

Last week Oleksiy Danilov, secretary of Ukraine’s National Security and Defence Council, also warned that Russia was preparing a wave of offensives to mark the anniversary of the 24 February invasion.

He claimed Russian troops had been given the task of going “beyond the borders” of the eastern Donetsk and Luhansk regions.

Donetsk and Luhansk make up the Donbas, a region bordering Russia that President Vladimir Putin identified as a goal for takeover from the war’s outset.

Luhansk governor Serhiy Haidai has claimed that Russian forces are expelling residents near the Russian-held parts of the front line so they can’t tell Ukrainian artillery forces about troop deployments.

“There is an active transfer of [Russian troops] to the region and they are definitely preparing for something on the eastern front in February,” Haidai said.

Ukraine’s defence minister was in France to meet President Emmanuel Macron and secure the purchase of air defence radars. He was also lobbying European nations to send F-16 fighter jets to Ukraine, something Macron said his country had not ruled out.

“We tell our partners that we too must be ready as soon as possible,” Reznikov told French media. “That’s why we need weapons to contain the enemy.”

Intelligence experts and analysts have long suggested that a renewed offensive would probably be launched by Russia before spring. Much of the fighting in the country’s east has been in a state of deadlock for many weeks, with both sides reportedly enduring huge casualties as they become bedded in.

Late on Wednesday, at least three people were killed in the eastern city of Kramatorsk after a Russian missile strike destroyed a residential building.

“At least eight apartment buildings were damaged. One of them was completely destroyed,” police said in a Facebook post. “People may remain under the rubble.”

Regional governor Pavlo Kyrylenko posted a picture that appeared to show a four-storey building in Kramatorsk that had suffered major damage.

“This is not a replay of the past, it is the daily reality of our country – a country with absolute evil on its borders,” President Volodymyr Zelenskiy wrote on Telegram after the attack.

In a separate tweet, Zelenskiy wrote: “The only way to stop Russian terrorism is to defeat it. By tanks. Fighter jets. Long-range missiles.”

Reuters contributed to this report