The Ukrainian military has said a US-made F16 fighter jet provided by Western nations crashed during a combat mission, killing its pilot. The announcement was the first by the military describing a crash since it began receiving the jets.

Ukraine's General Staff said on Thursday that communication with one of F16 jets was lost as it was countering a Russian missile strike. It said it later found that the plane had crashed and the pilot was killed.

The Wall Street Journal earlier reported the crash occurred on Monday. The US newspaper quoted US officials as saying that initial reports indicated the jet was not shot down by enemy fire. US officials have warned about the dangers of sending pilots inexperienced on F16s into combat.

The US newspaper said losing one of the country's few F16s was a major blow for Kyiv.

Ukraine has been appealing to western nations for F16s, claiming they are indispensable in its fight against Russian forces.

Ukrainian President Volodymyr Zelenskyy confirmed the arrival of F16s on August 4. He said on Tuesday that the jets were used to repel Russia's attack the previous day.