Russia has issued a warning to South Korea against sending arms to Ukraine, with Deputy Foreign Minister Andrey Rudenko calling on Seoul to "soberly assess the situation and refrain from reckless steps".

The Ukrainian military said on Monday that it found Western-made parts inside North Korean ballistic missiles, marking the latest discovery for Kyiv as it continues to find technology from Europe and the US inside weapons used by the Russian military.

North Korea is expanding a key weapons manufacturing complex that assembles a type of short-range missile used by Russia in Ukraine, researchers at a U.S.-based think tank have concluded, based on satellite images.