Sri Lanka, Jan. 28 -- Russia's grinding invasion of Ukraine has caused nearly two million military casualties -- killed, wounded or missing -- between the two countries, according to a study published Tuesday by a US think tank.

Moscow's forces have borne the brunt of the losses, suffering as many as 325,000 killed out of an estimated total of 1.2 million casualties since invading Ukraine nearly four years ago, the Center for Strategic and International Studies (CSIS) found.

"No major power has suffered anywhere near these numbers of casualties or fatalities in any war since World War II," CSIS said, noting that "Russian forces are advancing remarkably slowly on the battlefield."

Ukrainian forces have also suffered major losses -- betw...