NATO Secretary General Jens Stoltenberg said the Ukrainian Armed Forces' operation in Kursk region is legal and Ukraine has the right to self-defense under international law, Reuters said.

"Ukraine's incursion into Russia's Kursk region is legitimate and covered by Kyiv's right to self-defence. Ukraine has a right to defend itself. And according to international law, this right does not stop at the border," he told the German weekly Welt am Sonntag.

Additionally, he said NATO was not informed in advance about Ukraine's plans and did not play any role in them.

Stoltenberg said Ukraine is at risk due to the offensive on Russian territory, but Kyiv must decide how to conduct its military campaign.

"President [Volodymyr] Zelenskyy has made clear that the operation aims to create a buffer zone to prevent further Russian attacks from across the border. Like all military operations, this comes with risks. But it is Ukraine's decision how to defend itself," he said.

As reported, Ukrainian forces confirmed advancing up to ten kilometers into Russia's Kursk region on August 6 and 7, amid ongoing mechanized offensives into Russia on August 7, according to an August 7 report from the Institute for the Study of War (ISW).