(Bloomberg) -- South Korean President Yoon Suk Yeol warned Russia and North Korea against making any arms deals, saying Seoul and its allies would be ready to respond to the “direct provocation.”

South Korean officials have said North Korean leader Kim Jong Un’s recent trip to Russia could have been aimed at furthering a transfer of arms to help Moscow in its invasion of Ukraine. Yoon used an address Wednesday at the United Nations General Assembly to warn that military cooperation between the two would be a global concern.

Yoon said if the North acquires the information and technology necessary to enhance its weapons of mass destruction capabilities in exchange for supporting Russia with conventional weapons, that “will be a direct provocation threatening the peace and security of not only Ukraine but also the Republic of Korea,” referring to his country by its formal name.

Seoul “together with its allies and partners, will not stand idly by,” he said, adding this could lead to calls to reform the UN Security Council. 

Separately, Ukrainian President Volodymyr Zelenskiy lashed out at Russia in his first in-person address to the Security Council on Wednesday, calling for Moscow to be stripped of its powerful veto as one of the permanent members of the UN’s top decision-making body. 

The US has for months accused Kim of providing arms and ammunition to aid President Vladimir Putin’s war, including sending shells and rockets. While the US has said the weapons aren’t likely to alter the battlefield, they can aid in the bombardment of Ukraine, while sales could provide North Korea with a new stream of revenue for an economy isolated from much of world trade. 

A South Korean presidential official earlier this month said North Korean weapons have been used for a long time by Russia against Ukraine. 

Russia and North Korea have denied any arms deals, although Kim spent a large portion of his visit to Russia meeting military officials and touring weapons plants. In July, Kim gave a tour of North Korea’s latest weapons to Russian Defense Minister Sergei Shoigu when he made a rare visit to Pyongyang.

Read: Seoul Ships Arms to Poland as Ukraine Enlists Support From Asia

South Korean government policy prohibits lethal aid to countries at war. But Ukraine’s ambassador to South Korea, Dmytro Ponomarenko has said it’s time for a change, adding there’s a lot in its arsenal that could help Kyiv.

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