NATO was not involved in Ukraine's surprise offensive into the Russian region of Kursk, NATO chief Jens Stoltenberg has told the German newspaper Die Welt.
"Ukraine did not preview its planning for Kursk with NATO, and the alliance played no role," he said in the interview published on Saturday.
Some 10,000 Ukrainian troops crossed into the western Russian region on August 6. Kiev claims to control about 100 settlements and more than 1,000 square kilometres of Russian territory.
Ukrainian President Volodymyr Zelensky said the purpose of the push into Kursk is to create a buffer zone to halt attacks by Moscow on the Ukraine's hard-hit Sumy region.
Moscow accuses NATO states of supporting Kiev in its invasion by supplying weapons and ammunition to the Ukrainian military, as well as intelligence data.
Stoltenberg described Ukraine's advance across the border as legitimate.
"For over 900 days, Russia has waged an unprovoked war of aggression against Ukraine, and has conducted countless attacks on Ukraine from over the border in Kursk. The Russian soldiers, tanks and bases there are legitimate targets under international law," he told the newspaper.
"Like all military operations, this comes with risks. But it is Ukraine's decision how to defend itself."
While Moscow has struggled to put a stop to Kiev's counter-invasion, Russian troops have recently seized a string of settlements as they advance farther into the eastern Ukrainian region of Donetsk.
Heavy fighting is occurring near Pokrovsk, a strategically important city that is home to a railway junction. If Pokrovsk falls, it could set the stage for Russian advances toward bigger urban centres and bring Moscow closer to controlling all of the Donetsk region.
