Volodymyr Zelensky has marked the 500th day of the Ukraine war by posting a video from an island that turned into a symbol of Ukrainian resistance.

Toward the beginning of the war, Ukrainian soldiers defending Snake Island famously defied an order from a Russian warship to surrender.

The Black Sea island was seized by Russia but later reclaimed by Ukraine.

In a video, the Ukrainian president considered it a "place of victory" that would never be reconquered.

In the updated clip, posted on Telegram, Mr Zelensky described it as confirmation that Ukraine would return every last bit of its territory taken by Russia since the full-scale invasion started on 24 February 2022.

"I want to thank from here, from this place of victory, each of our soldiers for these 500 days," Mr. Zelensky said in the video, in which he was shown arriving on the island by boat and leaving flowers at a memorial.

The Ukrainian president later announced he had returned from a visit to Turkey with five commanders captured by the Russians during last year's siege of the Azovstal steel plant in Mariupol.

They had been in Turkey since September 2022 after being freed from Russian captivity as part of a wider prisoner exchange.

The circumstances of their homecoming are unclear, as the original deal obliged them to remain in Turkey.

Kremlin spokesperson Dmitry Peskov told Russian news agency RIA that Moscow had not been notified of the prisoner release, Reuters news agency reported.

"No one informed us about this," he was quoted as saying. "According to the agreements, these ringleaders were to remain on the territory of Turkey until the end of the conflict."

Mr. Peskov said the prisoner release came about because of pressure on Turkey from Nato ahead of a meeting next week.

Russia's Black Sea Fleet flagship Moskva sailed to Snake Island within hours of the start of the war and ordered Ukrainian soldiers on the island to give themselves up.

"I suggest you lay down your weapons and surrender to avoid bloodshed and needless casualties. Otherwise, you will be bombed," said a Russian officer.

The Ukrainian response and verbal exchange went viral as a soldier replied by telling the Russian warship to "go to hell" - although in far cruder language.

Snake Island was seized and the Ukrainian soldiers were taken prisoner - but later exchanged for Russian captives.

Ukrainian forces recaptured the island in June last year.

The deputy head of the UN's human rights monitoring team in Ukraine, Noel Calhoun, said the 500th day was "another grim milestone in the war that continues to exact a horrific toll on Ukraine's civilians".

The UN estimates more than 9,000 civilians, including some 500 children, have been killed since the war began, although it said the real number could be much higher.

Mr Zelensky made his video address after spending time visiting European leaders ahead of Nato's summit in Vilnius next week where the Ukraine war is expected to be high on the agenda.

He also welcomed the news that the US would be supplying Ukraine with cluster bombs - a weapon that has been banned in more than 120 countries because they have a record of killing civilians.

Both Ukraine and Russia have been using cluster munitions throughout the war, but the US's decision has proved controversial.

Mr. Zelensky called the latest US arms package "timely, broad and much-needed", tweeting that it "will provide new tools for the de-occupation of our land".