A rare Sukhoi S-70 Okhotnik—the Russian air force’s first stealthy armed drone— got shot down apparently by an accompanying Russian fighter after the drone seemingly malfunctioned near the Ukrainian-held fortress town of Chasiv Yar in eastern Ukraine on Saturday.

Ukraine’s air force said in a statement that air defenses had destroyed 56 of the 87 drones and two missiles over 14 Ukrainian regions, including the capital, Kyiv.

Ukraine on Sunday said it sent more than 100 drones deep inside Russia to hit a major weapons depot, as it stepped up attacks further inside Russian territory.

Russia unleashed an overnight drone attack across Ukraine targeting the capital, Kyiv, and hitting infrastructure in the Black Sea port of Odesa, Ukrainian officials said Sunday.

Ildar Dadin, a well-known Russian opposition activist who was fighting in Ukraine on the side of Kyiv, has been killed in action, according to the group that recruited him. A spokeswoman for that group,

Russian air attacks on Ukraine kept the eastern half of the country under air raid alert for more than five hours, Ukraine's military said early on Sunday, with Moscow launching several waves of strikes targeting Kyiv and other cities.

"The enemy is deploying personnel there," said Vladyslav Voloshyn, a spokesperson for Kyiv's forces operating in southeast Ukraine.