“Commander of the Kostroma Airborne Regiment, Colonel Sergei Sukharev…got lost in the ‘[military] exercises’, but returned home the right way,” said the Ukrainian statement.

His deputy Major Sergei Krylov was killed alongside him, said the report.

They were among a number slain from the Kostroma regiment, seen as among Russia’s most elite fighting forces.

Russia acknowledged that senior sergeant Sergei Lebedev, sergeant Alexander Limonov and corporal Yuri Degtyaryov were also killed.

Sukharev was seen on Russian TV in January when he led his troops back from Kazakhstan where they had been sent following a wave of protests.

Russia described their mission as “peacekeeping” and Sukharev said his forces protected a vital power plant in Almaty.

Also killed in the latest Ukrainian fighting was military intelligence officer Sergey Vishnyakov, of the GRU’s 22nd Separate Special Forces Brigade. He is believed to have been killed fighting near Mariupol in a Grad attack by Ukraine’s Azov battalion.