Russia has lost its ninth colonel in battle since the Ukraine invasion began in February.
Colonel Alexander Bespalov, who was commander of the 59th Guards Tank Regiment, was killed "during a special military operation", according to a local announcement.
A funeral was held for Bespalov in the central city of Ozersk in Russia on Friday (local time) but no details have been given about his death.
Earlier, Kremlin spokesman Dmitry Peskov said the casualties from the Ukraine invasion, which began on February 24 were "a huge tragedy for us".
It comes after at least 50 people were killed and many more wounded in a strike on a railway station in Kramatorsk that was packed with civilians hoping to flee the threat of a major Russian offensive, Ukraine said.
The US believes Russia used a short-range ballistic missile to strike the railway station on Friday, a senior United States defence official said.
According to the UN, 11 million Ukrainians - more than a quarter of the population - have fled their homes while more than 4 million of those people have left the country altogether.
