North Korea has criticized the United States for expanding its military aid to Ukraine, reports "Reuters".
Pyongyang's position is a confirmation of the isolated country's support for Moscow in the war in Ukraine.
Washington and Seoul are increasingly alarmed by deepening military cooperation between Russia and the North, and accuse them of violating international law by trading weapons for Russia to use against Ukraine. However, Moscow and Pyongyang deny these claims.
Under an agreement signed by Russian President Vladimir Putin and North Korean leader Kim Jong Un during Putin's visit to Pyongyang last week, each side pledged to provide immediate military assistance to the other in the event of armed aggression against either is one of them.
Today, Putin thanked Kim for his hospitality during the visit, which raised ties to an unprecedented level, the Kremlin said.
Analysts say the pact will frame the arms trade between the two countries and strengthen their anti-American sentiment and anti-Western coalition.
Park Jong-chon, one of North Korea's top military officials, said Russia had "the right to choose any kind of retaliatory strike". He pointed out that if Washington continues to push Ukraine towards a "proxy war" against Russia, this could provoke a stronger response from Moscow and lead to a "new world war".
He referred to Pentagon comments last week that Ukrainian forces could use US-supplied weapons to strike Russian forces anywhere within Russia's borders.
Senior officials of South Korea, the US and Japan condemned "in the strongest possible way" the deepening of military cooperation between North Korea and Russia in a joint statement released by Seoul's foreign ministry today.
Russia likely received about 1.6 million artillery shells from North Korea from August to January. According to the US non-profit security organization C4ADS, 74,000 tons of explosives have been moved from Russian ports in the Far East to other sites, mostly along the borders near Ukraine.
The US says Putin's mutual defense deal with North Korea has the potential to create friction with China, long the isolated country's main ally.
North Korea plans to send construction and engineering forces to the Russian-occupied territories of Ukraine as early as next month for reconstruction work, a representative of the South Korean government announced earlier.
These forces, working abroad as construction workers to earn hard currency for the regime, will be relocated from China to Russian-controlled areas.