An adviser to President Volodymyr Zelenskyy of Ukraine has said that 10,000 to 13,000 of the country’s soldiers have been killed since Russia invaded, offering a rare government assessment of the casualties.

Neither Moscow nor Kyiv has offered much detail on their numbers of dead and wounded troops since the war began in late February. But Western analysts say that both sides have sustained heavy losses.

The presidential adviser, Mykhailo Podolyak, told a Ukrainian news station late Thursday that “official figures” from the military put the number at between 10,000 and 12,500 to 13,000 killed, according to The Associated Press. He said that the number of injured Ukrainian troops was even higher, the AP reported.

There was no immediate comment or confirmation from the Ukrainian military, which has largely refrained from offering its own casualty numbers, though it frequently posts updates about Russian losses.

In August, Gen. Valeriy Zaluzhnyi, commander of Ukraine’s armed forces, said that about 9,000 of his country’s soldiers had been killed at the front. Since then, however, Ukraine has waged a series of counteroffensives to reclaim territory from Russian forces in the northeast and south of the country.

The top U.S. general, Mark Milley, chair of the Joint Chiefs of Staff, said last month that more than 100,000 of Moscow’s troops had been killed or wounded in the war and that Ukraine had probably suffered a similar number of casualties.

The president of the European Commission, Ursula von der Leyen, attracted criticism this week for posting, and then deleting, a video in which she said that 100,000 Ukrainian troops had been killed. Her spokesperson responded later on Twitter, saying that the video had been taken down because Von der Leyen’s comments were inaccurate and the figure referred to dead and wounded.

This article originally appeared in The New York Times.