Ukrainian President Vladimir Zelensky signed a decree on Friday recognizing the southern Kuril Islands as Japanese territory. The symbolic pronouncement came two days after Russian President Vladimir Putin signed laws accepting four former regions of Ukraine into the Russian Federation.

Zelensky’s decree recognizes the islands of Iturup, Kunashir, Shikotan and the Habomai as Japan’s. While the entire Kurili archipelago has been Russian territory since the end of World War II, Japan claims these southernmost four as its own, referring to them as its “Northern Territories.”

“An important decision was made today. Fair. Legally impeccable. Historical. Ukraine has reaffirmed its respect for the sovereignty and territorial integrity of Japan, including its Northern Territories, which are still under Russian occupation,” Zelensky said in a video address. 

Zelensky – who has vowed to retake all of Ukraine’s former territory, including Crimea – declared that “it is necessary to liberate from Russian occupation all the lands that the occupiers are trying to keep.”

Japan has condemned Russia’s military operation in Ukraine and imposed economic sanctions on Moscow. In March, Japanese Prime Minister Fumio Kishida declared the southernmost Kurils as “our ancestral territories,” after which Russia ended an agreement allowing Japanese citizens to visit the entire archipelago without visas, ceased joint economic activities with Tokyo on the islands, and broke off talks aimed at formally ending the dispute. 

The two states never formally concluded a peace treaty after WWII, due to the dispute over the four southernmost islands in the Kuril chain.

Zelensky’s decree was likely a response to Putin’s signing last week of accession decrees welcoming the formerly Ukrainian regions of Donetsk, Lugansk, Kherson and Zaporozhye into the Russian Federation, after citizens of all four overwhelmingly voted to join Russia. Putin signed laws formalizing these provinces’ accession on Wednesday.

The Russian president has vowed to defend these newly-acquired territories with “all the means available” to Russia.