KYIV (Reuters) - Ukraine has lost over 40% of the territory in Russia's Kursk region that it rapidly seized in a surprise incursion in August as Russian forces have mounted waves of counter-assaults, a senior Ukrainian military source said.

Ukraine has lost more than 40 per cent of the territory in Russia’s Kursk region that it seized in August, a senior Ukrainian military source said. Russia had deployed 59,000 troops to the region since the surprise invasion by Kyiv’s forces,

Tit-for-tat moves this week included the use of American-made ballistic missiles to strike inside Russia, and new nuclear threats from Moscow. Neither appear to have influenced the war on the ground.

In a stark warning to the West, President Putin said the attack with the intermediate-range Oreshnik missile was in retaliation for Kyiv’s use of U.S. and British longer-range missiles.

Another dangerous escalation in the Ukraine war. Russia has confirmed they launched a new missile into Ukraine.