"We think that the total number of DPRK forces in Russia... could be closer to around 11 to 12,000," with "at least 10,000 right now in the Kursk Oblast," Pentagon spokesman Major General Pat Ryder told journalists, using an abbreviation for North Korea's official name.

Top US officials had last week put the number of Pyongyang's soldiers in Kursk -- where Ukrainian troops have been conducting a ground offensive since August and control several hundred square miles of Russian territory -- at about 8,000 out of a total of 10,000 in Russia.

Ryder said he expected other North Korean troops in Russia to likewise be sent to Kursk, but added that the Pentagon could not at this point confirm reports that they have entered combat.

Russia and North Korea have deepened their political and military alliance as the Ukraine war has dragged on, and the prospect of Pyongyang sending troops into combat against Ukraine's forces has sparked widespread international concern.