KYIV: Three Ukrainian pilots died after two L-39 trainer aircraft collided over a region west of the capital on Friday, the country's air force said in a statement on Saturday.

President Volodymyr Zelenskiy, who is counting on swift training of Ukrainian crews to fly up to 61 F-16 fighter jets promised by his Western allies, said the three men included Andriy Pilshchykov, "a Ukrainian officer, one of those who greatly helped our state."

The investigation is ongoing, he added in his nightly video address. "It is too early to discuss details. Certainly, all circumstances will be clarified."

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The air force said the crash occurred in Zhytomyr region in central Ukraine. Pilshchykov, who used the callsign "Juice," had become well known after giving numerous interviews to international media, it said.

"We express our condolences to the families of the victims. This is a painful and irreparable loss for all of us," the air force wrote on the Telegram app.

Zelenskiy offered condolences to the pilots' families and added, "Ukraine will never forget anyone who defended the free skies of Ukraine."