Ukraine President Volodymyr Zelensky says he has returned Poland's highest honour after his Polish counterpart Karol Nawrocki said he was stripping him of the award.

The Polish Order of the White Eagle was bestowed on Zelensky in 2023 by then-President Andrzej Duda.

But Kyiv caused outrage last month after renaming a Ukrainian army unit after a group of controversial World War Two fighters called the Ukrainian Insurgent Army (UPA).

Three senior Ukrainian officials have also said they are returning awards bestowed by Poland, to show solidarity with their president.

Many in Ukraine regard the UPA, which existed in the 1940s and 1950s, as heroes who fought for Ukrainian independence against the Soviet Red Army, Nazi Germany and Polish authorities. The group's red and black flag is often used by Ukrainian troops on the front line today.

Poland, however, accuses the UPA of carrying out a genocide of about 100,000 ethnic Poles in Volhynia (now Volyn in Ukraine) in 1943-45.

In a statement on social media, Zelensky said Ukraine would "remain open to all meaningful formats of engagement with Poland in order to try to avoid conflicting interpretations of the difficult and painful chapters of our shared past".

He added Ukraine was "grateful to the Polish People for their support and co-operation".

Poland has been one of Ukraine's main allies during the war against Russia, taking in hundreds of thousands of refugees and serving as a logistics hub for aid to Ukraine.

Polish President Karol Nawrocki branded Ukraine's decision late last month to name the unit after the UPA "outrageous", "incomprehensible" and "deeply disappointing".

"For the overwhelming majority of Polish society, the UPA remains, above all, a formation responsible for the brutal crimes committed against citizens of the Republic of Poland during World War Two," Nawrocki said in a video released on the president's official website.

"It hurts not only our historical memory. It also undermines the trust built up over the years and in recent months," he added.

However, Nawrocki stressed the diplomatic row would not impact Poland's support for Ukraine against Russia.

Polish Prime Minister Donald Tusk said on social media that any feud between the two "delights" Russia's Vladimir Putin and called on Zelensky and Nawrocki to "calm emotions, not to stoke tensions".

Ukraine has ambitions to become an EU member state and attended the first phase of membership negotiations this week in Luxembourg.