As many as 1.6 million people may have already been taken from Ukraine to Russia against their will since the war in Ukraine began, according to the US State Department on Wednesday.
The department said "estimates from a variety of sources" indicate that between 900,000 and 1.6 million Ukrainian citizens, including 260,000 children, were taken from their homes.
Many were taken to "isolated regions in the Far East," a statement said.
The US called on Russia to immediately end "systematic 'filtration' operations and forced deportations" in Russian-controlled areas in Ukraine.
These constituted a serious violation of the Fourth Geneva Convention pertaining to the Protection of Civilian Persons in Time of War, it said.
Russia must release detainees and allow Ukrainians who have been forced to leave their country to return home, the State Department demanded.
