Ukraine has lost more than 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 counterassaults, a senior Ukrainian military source said.

Of the territory Ukraine captured in a surprise attack in Russia's Kursk oblast in August, it has already lost 40 percent again. An army source told the Reuters news agency. “At the maximum, we had control of 1,

Ukraine has lost over 40 percent 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 counterassaults, a senior Ukrainian military source has said.

The Kursk offensive was the first ground invasion of Russia by a foreign power since World War Two and caught Moscow unprepared.

Meanwhile, Ukraine's surprise incursion into Russia's Kursk region is faltering. Russian troops have pushed Kyiv's offensive backwards. Experts have questioned the success of the offensive, with one calling it a "strategic catastrophe" given manpower shortages faced by Ukraine.

The move marks the latest reversal from the White House on what weapons it’s sending and how freely Ukraine can use them.