KYIV, UKRAINE -- Ukrainian authorities have launched an investigation after a midair collision between two warplanes in the west of the country killed three pilots.

Ukraine's air force spokesman Yuri Ihnat told Ukrainian television on Sunday it wasn't immediately clear how long the probe would take.

According to the air force's Telegram page, two L-39 training military aircraft collided on Friday during a combat mission over Ukraine's western Zhytomyr region. Three pilots were killed, including Andriy Pilshchykov, a well-known pilot with the nickname "Juice" who was an outspoken advocate for Ukraine getting F-16 fighter jets.

President Volodymyr Zelenskyy in his nightly address on Saturday paid tribute to Pilshchykov, describing him as a "Ukrainian officer, one of those who helped our country a lot."

Ukraine's Vasilkiv tactical aviation brigade on Sunday identified the other two pilots killed in the collision as Viacheslav Minka and Serhiy Prokazin.

Russian forces, in the meantime, targeted central and northern regions of Ukraine with cruise missiles overnight. Ukraine's air force on Sunday reported air defences successfully intercepted four of them. In the Kyiv region surrounding the Ukrainian capital, the falling debris damaged a dozen private homes and wounded two people, Ukraine's Interior Ministry said.

Russia's Defense Ministry said in a statement Sunday that it targeted -- and successfully hit -- an airfield in the Kyiv region. Ukrainian officials did not immediately comment on the claim.

In Kyiv, relatives of soldiers captured by Russian forces in Mariupol, a port city in eastern Ukraine Moscow's army besieged and seized early on in the war, gathered for a rally marking 500 days since their family members were in captivity. They demanded that the Ukrainian authorities bring their loved ones home.

In Russia, the Defense Ministry reported bringing down two drones over the Bryansk and Kursk regions that border Ukraine. The drones, the ministry said, were launched by "the Kyiv regime" in "yet another attempt at terrorist attacks" on Russian soil.

Kursk Gov. Roman Starovoit, however, reported that a drone slammed into a multistory residential building in the region's namesake capital. It wasn't immediately clear if it crashed after being shot down by air defences, like the Defense Ministry reported, or was targeting the building. Starovoit said no one was hurt, but a number of windows were shattered.

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Dasha Litvinova contributed to this report from Tallinn, Estonia.