Colonel General Oleksandr Syrskyi, commander in chief of Ukraine’s armed forces, said that Ukrainian successes in Sumy had prevented Russia from deploying about 50,000 Russian troops, including elite airborne and marine brigades, to other areas of the front line.

His claim could not be independently verified, and Russian officials made no immediate comment.

In March, Ukrainian forces withdrew from much of Russia’s neighbouring Kursk region, parts of which they had controlled after a surprise cross-border attack in August.

That retreat enabled Russia to launch a counteroffensive that advanced between 2km to 12km into Ukrainian territory, according to different estimates.

Ukrainian officials say fierce fighting is also taking place in the eastern Donetsk region.

The Russian Defence Ministry said on Thursday that its forces had captured two villages, Novoserhiivka and Shevchenko, in Donetsk.

Capturing Shevchenko marked an important stage in Russia’s ongoing offensive that is trying to break into Ukraine’s Dnipropetrovsk region, which borders Donetsk and is a major industrial centre, according to the ministry.

Meanwhile, the two sides continued to launch long-range strikes.

The Russian ministry said 50 Ukrainian drones were downed over nine regions overnight, including three over the Moscow region.

Ukraine’s air force said that Russia deployed 41 Shahed and decoy drones across the country overnight, wounding five people. It said that 24 drones were either intercepted or jammed.