The Kremlin warns Kyiv's use of such missiles would mark an escalation in the conflict, hours after Joe Biden gives the green light.

Russia says the use of US long-range missiles by Ukraine will lead to "an appropriate and tangible" response. Such an attack inside Russian territory "would represent the direct involvement of the United States and its satellites in hostilities against Russia", a foreign ministry statement said.

Ukraine has been pleading with the US for months to let it use American-made weapons to hit military targets inside Russia beyond the border zone. Now, as he nears the end of his presidency, Joe Biden has relented and decided to lift some restrictions,

The United States said on Monday it was Russia that is escalating the conflict in Ukraine by deploying North Korean troops, after the Kremlin warned that Washington would deepen its involvement in the war by allowing Kyiv's forces to strike far into Russia with U.

Russia is paying $2,000 a month for each North Korean soldier, per reports. But the soldiers, who could number 100,000, probably won't see any of it.

North Korea ratified a major defence pact with Russia on Tuesday, outlining mutual military aid and requiring both countries to provide each other with immediate military assistance if attacked. Russia had already completed its side of the ratification last week after the pact was signed by Russian President Vladimir Putin and North Korean leader Kim Jong Un.