Ukrainian Ground Forces Command spokesperson Lieutenant Colonel Volodymyr Fityo has said that 11,000 Russian soldiers were killed in November.
The troops were likely killed in the Kupyansk, Lyman, and Bakhmut directions, according to the US-based Institute for the Study of War think tank.
The institute also said Russian forces “may be suffering losses along the entire front in Ukraine at a rate close to the rate at which Russia is currently generating new forces.”
Earlier Lord David Cameron, the UK foreign secretary, said the US not sending more war aid to Ukraine would be a “Christmas present” for Vladimir Putin and Xi Jinping after US Senate Republicans opposed a multi-billion-dollar aid bill.
He urged allies to rally around Kyiv, describing the response to the conflict as “the great test for our generation”.
The US Congress failed to pass a $110bn (£88bn) package of wartime funding for Ukraine and Israel as well as other national security priorities. Republicans have suggested more money needs to be allocated to securing the US border with Mexico.