Volodymyr Zelensky has intensified his call for the international security system to be overhauled as new evidence emerged of alleged crimes by Russian forces in areas that were recently recaptured by Ukrainian troops.

The Ukrainian president intensified his criticism of the global community in a late-night video address after lambasting the UN for failing to prevent Russia’s invasion of the country in a speech to the UN Security Council on Tuesday.

Ukrainian forces have largely managed to repel Russia’s onslaught in many parts of the country, including around the capital Kyiv after more than a month of fighting.

But the retreat of Russian troops has revealed a trail of destruction and growing evidence of civilian killings and war crimes in Irpin, Bucha and Borodyanka, areas near the capital that were under Russian occupation until last week. Russia has denied the allegations.

The EU and US are preparing a package of additional sanctions on Moscow following reports of the atrocities. EU member states on Wednesday will discuss a ban on coal imports into the bloc and Washington is planning to bar new investment into Russia and tougher restrictions on the country’s financial institutions, state-owned enterprises and government officials.

European governments, including Italy and Spain, expelled 90 Russian diplomats on Tuesday, after similar moves by Germany, Poland and Slovakia in recent days. It was also revealed the Czech Republic had sent tanks and infantry fighting vehicles to Ukraine, to bolster its defences as Russia refocuses its military offensive on the south and east of the country.

Zelensky has called for Russia’s leaders to be “brought to justice” and sharply criticised the UN Security Council, of which Russia is permanent member with the power to veto any decision.

“The UN Security Council exists and security in the world doesn’t,” he said in a video address on Tuesday. The president added that the UN “was unable to carry out the functions for which it was created” because Russia was able to block decisions as a permanent Security Council member with the ability to veto any actions.

“I hope the world will draw conclusions,” he added. “Otherwise there will be only one institution left in the world to guarantee the security of states. Namely — weapons.”

Zelensky made his comments as more territory was freed from Russian control and indications emerged of further atrocities. During a visit to Irpin and Bucha on Tuesday, some of Kyiv’s satellite cities which have been recently freed, mangled tanks and charred armoured vehicles were testimony to heavy fighting.

In Irpin and Bucha, residents displayed the makeshift graves of civilians allegedly killed by Russian forces, as destroyed buildings and bridges revealed the scale of the conflict in recent weeks.

“They bombed locals while they were being evacuated. People here talk about civilians being executed. The Russians even drove tanks over the shot bodies. And we had to shovel away the remains of these people,” Oleksandr Markushin, the mayor of Irpin, told the Financial Times.

“A mine exploded right in front of me, and two children, a mother and one volunteer died right on the spot,” he said. “The war must be stopped. But it must be stopped on the terms that will be beneficial to Ukraine. We paid a very high price for this war.”

Authorities said Borodyanka, a town west of Irpin, was flattened. “Today, there are so many war crimes that they go beyond qualification,” Iryna Venediktova, Ukraine’s chief prosecutor, said. “These are crimes against humanity that have been systematically committed by Russians. We can work out Irpin, Bucha, Vorzel, but, in fact, the worst situation in terms of victims is in Borodyanka.”

Zelensky also said that his government was “preparing” to welcome Ursula von der Leyen, president of the European Commission, and the EU’s top diplomat Josep Borrell, to Kyiv “in the near future”.

“Working together in Kyiv is something that will be praised by many nations of the world. And not only in Europe,” he said. “Because now Kyiv is the capital of global democracy, the capital of the struggle for freedom for all on the European continent.”