Russia has sharply criticised Japan over its decision to lend Ukraine more than $3bn, calling the move "treacherous" and accusing Tokyo of participating in what it described as the theft of Russian sovereign assets, Japan Today reports.

The condemnation follows an agreement signed on April 18 in Washington, under which Japan will provide Ukraine with a loan worth approximately JPY471.9bn ($3.3bn). Notably, the funds used to guarantee the loan will be drawn from profits generated by Russian assets frozen in the European Union – assets long-immobilised in the wake of Moscow’s full-scale invasion of Ukraine in 2022.

The funds are part of a broader initiative by the Group of Seven (G7) nations known as the Extraordinary Revenue Acceleration (ERA) programme. This framework aims to provide Ukraine with $50bn in reconstruction aid, largely financed by interest generated from frozen Russian central bank reserves.

Speaking in Moscow on April 24, a Russian Foreign Ministry spokeswoman Maria Zakharova lashed out at Tokyo’s involvement in the scheme, warning that it would further damage already strained relations between the two nations.

“We have long warned the Japanese side that participation in illegitimate experiments with the sovereign assets of the Russian Federation in any form... will be regarded by us as complicity in theft,” Ms Zakharova told reporters according to the Japan Today report.

“Tokyo has cynically expressed its hope that these actions will not have a negative impact on relations with Russia. We have to disappoint them – such actions will certainly and inevitably have a negative impact on relations with Russia. We regard such a step as extremely hostile, as treacherous. It is inadmissible under both legal and universal concepts” she added.

Moscow has in recent decades made repeated moves to bully Japan into remaining silent on a number of territorial issues, most famously over possession of the Kuril Islands east of Hokkaido.

The strongly worded rebuke by Moscow underscores a deeper deterioration in Japan–Russia relations, which have been steadily unravelling since Russia’s annexation of Crimea in 2014 and reached new lows after the full-scale invasion of Ukraine. Japan, in lockstep with its Western allies, meanwhile, has imposed multiple sanctions on Russia, including financial restrictions and export controls, and has expressed repeated support for Ukraine’s sovereignty and territorial integrity.

Tokyo's participation in the ERA plan signals a significant evolution in its approach, moving beyond diplomatic support into direct financial assistance backed by frozen Russian assets. While EU leaders and US officials have largely framed the programme as a lawful use of proceeds – not the assets themselves – Moscow sees little distinction.

The response from Russia has been particularly fierce towards Japan, however, in part due to their already contentious bilateral history. The two countries have never formally signed a peace treaty to end World War Two hostilities, owing to the long-standing Kuril islands territorial dispute after the islands were captured by Soviet forces in the war’s final days.

Known as the Southern Kurils in Russia and the Northern Territories in Japan, these four islands off the coast of Hokkaido have been under Moscow’s control since 1945. Successive Japanese governments have pressed for their return, while Russia insists its sovereignty over the archipelago is non-negotiable. This impasse has been a perennial obstacle to closer diplomatic ties.

Earlier in April, Moscow declared that it saw no reason to revisit peace treaty discussions with Japan, citing what it called Tokyo's "unfriendly stance" and alignment with Western policies designed to isolate Russia.

In that context, the latest financial arrangement with Ukraine is being interpreted by the Kremlin as not only a diplomatic affront but a legal provocation. Russia maintains that the frozen assets remain the property of its state and their utilisation – even indirectly through interest – constitutes a violation of international norms.

Japanese officials have made no immediate public comment on the Russian statements, but former Prime Minister Fumio Kishida previously emphasised Japan's commitment to international law and support for Ukraine's recovery. Tokyo has contributed humanitarian aid and non-lethal military support since the outset of the conflict, but current PM Shigeru Ishiba is far more of an established figure, once billed as a defence-hawk of sorts for support in revising Japan's pacifist consitution. 

Observers say the sharp rhetoric from Moscow this time may reflect broader anxieties within the Kremlin over the precedent set by the G7’s actions and particularly its wealthy eastern neighbour Japan. If more economically powerful nations can repurpose immobilised sovereign assets or their proceeds for wartime recovery, Russia fears the approach could be replicated elsewhere – a scenario that would deepen its financial and geopolitical isolation.

For now, any hopes of a diplomatic thaw between Tokyo and Moscow appear distant. With the war in Ukraine grinding on and the global financial response growing more coordinated, Japan's involvement in Ukraine's recovery effort marks a new chapter in a relationship already marred by mistrust and historical grievances.