Ukrainian President Volodymyr Zelenskyy has said the Russian forces’ withdrawal from northern areas of the country was “slow but noticeable”, but he warned that Moscow was consolidating and preparing “powerful strikes” in the east and the south.

Zelenskyy said the situation in the country’s east was “extremely difficult”, with evacuations efforts under way for thousands of civilians trapped in besieged cities such as Mariupol.

“We are moving forward, moving carefully,” he said in his latest video address on Saturday.

Russia continued withdrawing some of its ground forces from areas around Kyiv after saying earlier this week it would reduce military activity near the Ukrainian capital and the northern city of Chernihiv.

On the outskirts of Kyiv, where Russian troops have withdrawn, damaged cars lined the streets of Irpin, a suburban area popular with young families, now in ruins. Emergency workers carried elderly people on stretchers over a wrecked bridge to safety.

But Zelenskyy warned his people that retreating Russian forces were creating “a complete disaster” outside the capital as they leave mines across “the whole territory”, including around homes and corpses.

“They are mining the whole territory. They are mining homes, mining equipment, even the bodies of people who were killed,” Zelenskyy said in his nightly video address to the nation. “There are a lot of tripwires, a lot of other dangers.”

Ukraine’s military said it had retaken 29 settlements in the Kyiv and Chernihiv regions.

Still, Ukraine and its allies warned that the Kremlin is not de-escalating to promote trust at the bargaining table, as it claimed, but instead resupplying and shifting its troops to the country’s east. Those movements appear to be the preparation for an intensified assault on the mostly Russian-speaking Donbas region in the country’s east, which includes Mariupol.

Zelenskyy warned of difficult battles ahead as Russia redeploys troops. “We are preparing for an even more active defence,” he said.

He said the situation in the east was “extremely difficult”, with Russia gathering its forces and “preparing for new powerful blows”. Ukraine was preparing an “active” defence, he added.

“I emphasise again, hard battles lie ahead. We cannot think we have already passed all the tests.”

Deepening humanitarian crisis

His statement also came as the humanitarian crisis in the encircled city of Mariupol deepened, with Russian forces blocking evacuation operations for the second day in a row.

Mariupol, the shattered and besieged southern port city, has seen some of the worst sufferings of the war. Its capture would be a major prize for Russian President Vladimir Putin, giving his country an unbroken land bridge to Crimea, seized from Ukraine in 2014.

About 100,000 people are believed to remain in the city, down from a pre-war number of 430,000. Weeks of Russian bombardment and street fighting have caused severe shortages of water, food, fuel and medicine.

“We are running out of adjectives to describe the horrors that residents in Mariupol have suffered,” Red Cross spokesman Ewan Watson said.

Zelenskyy said more than 3,000 people were able to leave Mariupol on Friday.

He said he discussed the humanitarian disaster with French President Emmanuel Macron by telephone and with the president of the European Parliament, Roberta Metsola, during her visit to Kyiv.

“Europe doesn’t have the right to be silent about what is happening in our Mariupol,” Zelenskyy said. “The whole world should respond to this humanitarian catastrophe.”

Zelenskyy did not say anything about the latest round of talks, which took place on Friday via video link. At a round of talks earlier in the week, Ukraine said it would be willing to abandon a bid to join NATO and declare itself neutral — Moscow’s chief demand — in return for security guarantees from several other countries.

The invasion has driven more than four million refugees from Ukraine.