Residents apply for Russian citizenship in Kherson on July 21, 2022, amid the ongoing Russian military action in Ukraine. AFP
Richard Moore, the head of Britain's MI6, said Thursday that the 15,000 dead was "probably a conservative estimate" and marked a "very bloody nose" for Putin who expected quick victory.
"That's probably a conservative estimate. That is the same number, roughly, as they lost in 10 years in Afghanistan in the 1980s," he told the Aspen Security Forum in the US Rocky Mountains.
"And these are not middle-class kids from Saint Petersburg or Moscow," he said.
"These are poor kids from rural parts of Russia. They're from blue-collar towns in Siberia. They are disproportionately from ethnic minorities. These are his cannon fodder."
CIA Director Bill Burns, speaking a day earlier at the same conference, said that US intelligence estimated Russian losses "in the vicinity of 15,000 killed and maybe three times that wounded."
"So quite a significant set of losses. The Ukrainians have suffered as well, probably a little less than that, but significant casualties," Burns said.
Ukraine has offered a much higher figure on losses inflicted on Russia, saying earlier this month that some 36,200 Russian personnel had died.
Russia has been deeply reticent and has given an official toll only twice, the last on March 25 with a figure of 1,351 which experts believe is far too low.