South Korean President Yoon Suk Yeol warned on Wednesday that his country and its allies “will not stand idly by” if North Korea receives Russian help to boost its weapons of mass destruction – just days after the leaders of the two nuclear-armed nations held a closely watched summit.

North Korean leader Kim Jong Un traveled to Russia last week for a meeting with President Vladimir Putin. Ahead of the meeting US officials warned that the two leaders could strike a deal that would provide weapons for Moscow to use in its grueling war against Ukraine – and that could see sanction-hit Pyongyang gain access to vital Russian technology.

Speaking at the United Nations General Assembly in New York, Yoon declared: “While military strength may vary among countries, by uniting in unwavering solidarity and steadfastly adhering to our principles, we can deter any unlawful provocation.”

He also called to reform the UN Security Council – of which Russia is a member – saying such a move “would receive a broad support” if Moscow did supply Pyongyang with information in exchange for weapons.

“It is paradoxical that a permanent member of the UN Security Council, entrusted as the ultimate guardian of world peace, would wage war by invading another sovereign nation and receive arms and ammunition from a regime that blatantly violates UN Security Council resolutions,” Yoon said.