Ukrainian forces appear to have retaken crucial territory east of Kyiv as they mount a counter-attack against invading Russian forces.

CNN reported the success, citing social media videos showing Ukrainian troops, along with captured Russian armour, in the small settlement of Lukyanovka, 55 kilometres east of the Ukrainian capital.

In one video, a Ukrainian soldier in Lukyanovka says: “The operation was completed, with absolute success, we knocked out the enemy.”

It came amid reports Russia’s advance on Kyiv has largely stalled, exactly a month after its invasion began, and that Moscow is struggling to resupply its forces. Russian troops are said to be low on morale and in danger of being surrounded north of the city.

US and British authorities have also assessed that Ukraine likely did conduct a successful attack against Russian ships in the Sea of Azov port city of Berdyansk.

On Thursday, Ukraine said it had destroyed the Orsk, a landing ship docked in Berdyansk port – in what would be a major blow to the Russians. Video from the city showed plumes of smoke pouring out of the dock area, as well as multiple explosions.

Only on Wednesday, Russia’s state-run RT media outlet had profiled the Orsk in Berdiansk port, saying it could carry 20 tanks or 40 armoured personnel carriers.

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On Friday, Ukrainian Deputy Prime Minister Iryna Vereshchuk also confirmed what she said was the first full-fledged swap of the month-old conflict.

They included some of the soldiers who became famous for telling a Russian warship to “go f— yourself” in the early days of the Ukraine invasion.

Ten of the soldiers who survived the subsequent bombardment of Snake Island were reportedly released in the biggest swap yet between the two nations. All were initially feared dead, before Russia confirmed the capture of some.

The exchange also freed 19 Ukrainian civilian sailors captured as their ship tried to take Ukrainian troops off Snake Island in late February.

Ukraine released 11 Russian civilian sailors as part of the deal, Ms Vereshchuk said. The civilians were rescued from a ship that sank near Odesa.

Don’t be late, Zelensky begs NATO

It came as NATO promised Kyiv new military support and assigned more troops to the alliance’s eastern flank. London and Washington have also stepped up sanctions on Moscow at a trio of summits aimed at showing Western unity against Russia’s war in Ukraine.

Leaders meeting in Brussels agreed to help Ukraine protect itself against any chemical, biological or nuclear attacks, and a US official said allies were working to provide Kyiv with anti-ship missiles.

However, support pledges by leaders from countries representing more than half of the world’s GDP fell short of satisfying Ukraine’s pleas for many more arms and tighter sanctions, including an embargo on Russian energy.

Speaking to 27 EU leaders via a video call on Thursday night, Ukrainian President Volodymyr Zelensky thanked them for sanctions against Russia but said they came too late to prevent Russian President Vladimir Putin from invading on February 24.

“Now we are discussing Ukraine’s membership in the European Union. At least here, I beg you, don’t be late,” Mr Zelensky said.

He called out Hungarian Prime Minister Viktor Orban for maintaining close ties with Mr Putin as Russia was shelling Ukrainian cities and hoped key sceptics of EU enlargement – Germany, France and the Netherlands – would change tack.

US President Joe Biden, who will visit a Polish town just an hour from the Ukraine border later on Friday, said: “The single most important thing is for us to stay unified and the world continue to focus on what a brute this guy is and all the innocent people’s lives that are being lost and ruined”, referring to Mr Putin.

“We have to stay fully, totally, thoroughly united.”

The US has promised to supply the EU with 15 billion cubic metres more of liquefied natural gas this year than had been planned before, sources told Reuters, as the European bloc seeks to quickly curb its reliance on Russian fossil fuels.

Russia supplies 40 per cent of the EU’s gas needs and more than a quarter of its oil imports.

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Those most dependent on this supply – in particular Germany – are reluctant to take a step that would have a major economic impact.

The Russian invasion has killed thousands and driven a quarter of Ukraine’s 44 million people from their homes.

Russian bombs have hit residential areas, schools and hospitals in Ukrainian cities, including Kharkiv and the besieged Azov Sea port of Mariupol.

“Putin has already crossed the red line into barbarism,” British Prime Minister Boris Johnson said as London announced restrictions on Gazprombank and Alfa Bank.

Canada and Australia also stepped up sanctions on Russia on Thursday as the war entered its second month. But the EU lacked the unanimous support needed to impose more punitive measures and was struggling to implement those already agreed.

NATO turned down pleas by Kyiv to defend Ukraine’s skies by imposing a no-fly zone and said again it will not send troops to the country for fear of being dragged into a full-on military confrontation with nuclear-armed Russia.

In a joint statement, leaders said they were “united and resolute in our determination to oppose Russia’s aggression, aid the government and the people of Ukraine, and defend the security of all allies”.

French President Emmanuel Macron said the world faced an “unprecedented food crisis” that will be even worse in 12-18 months as Ukraine, a major grower of wheat, barley, corn and sunflower, will not be able to sow crops.

NATO also warned China should “abstain from supporting Russia’s war effort in any way, and to refrain from any action that helps Russia circumvent sanctions”.

Mr Biden said China understood its economic future was more closely tied to the West than to Russia, after warning Beijing it could face consequences for aiding Moscow’s war.

-with AAP