The attack came as South Korea’s military said North Korea is preparing to send more troops to join Russia’s fight against Ukraine, despite Pyongyang suffering a high rate of losses among its existing deployment of 11,000 and seeing some of its soldiers captured.

Ukraine drones hit an oil refinery east of Moscow in a mass attack on Russia, according to military sources. The oil plant in Ryazan, 120 miles south east of the capital, was targeted, as was a microelectronics production plant in Bryansk, western Russia, according to Ukraine’s military.