North Korean troops have been deployed to a new Russian frontline region, a Ukrainian official said on Friday.

On October 23, US officials confirmed that North Korea had sent troops to Russia to help the country in its ongoing war against Ukraine, which began when Russian Pres. Vladimir Putin launched a full-scale invasion of Kiev in February 2022. At the same time, a North Korean representative has United Nations (UN) said last month that reports of Pyongyang sending troops to Moscow were “baseless rumours”.

On Monday, deputy Pentagon press secretary Sabrina Singh told reporters that it is likely that approximately 11,000 North Korean soldiers have entered Russia’s Kursk region. The Kursk region, which lies along Russia’s border with Ukraine, was the site of Kiev’s surprise incursion in August. Singh added that the North Korean troops “are moving into Kursk for a reason. We have every expectation that they would be engaged in combat operations.”

Andrii Kovalenko, head of Ukraine’s National Security and Defense Council’s Center for Countering Disinformation, wrote on Telegram on Friday that some North Korean troops have moved into the Belgorod region.

“Part of the military from North Korea was transferred to the border area of ​​the Belgorod region,” he wrote, using North Korea’s official name, the Democratic People’s Republic of Korea (DPRK). “There are none in the Kharkiv region.”

Belgorod Oblast is south of Kursk Oblast and opposite Kharkiv Oblast in Ukraine, which has Kiev’s second largest city, Kharkiv. The Russian city of Belgorod has been a target of Ukrainian strikes in the past.

Newsweek reached the Russian government via online forms and Ukraine’s Foreign Ministry via email for comment on Saturday afternoon.

Meanwhile, a senior Ukrainian military source told Reuters in an article published on Saturday that Ukraine has lost more than 40 percent of the territory it took in its surprise attack in the Kursk region late last summer.

“At most we controlled about 1,376 square kilometers (about 531 square kilometers), now this territory is of course smaller. The enemy is increasing its counterattacks,” said the unnamed source, who is in the General Staff of the Armed Forces of Ukraine.

The source added: “We now control about 800 square kilometers (about 309 square miles). We will hold this territory as long as it is militarily appropriate.”

President Joe Bidenmeanwhile, recently approved Ukraine will use US-supplied missiles deeper inside Russiaand granted a months-long request from the Ukrainian president Volodymyr Zelensky. The decision to allow Ukraine to use the Army Tactical Missile System (ATACM) further into Russian territory came amid the deployment of North Korean troops along Ukraine’s northern border.

North Korean troops in Russia signal growing ties between Putin and North Korea’s leader Kim Jong Un following the signing of a “comprehensive strategic partnership agreement” between the two countries in June.

The agreement, signed when Putin visited North Korea over the summer, says Moscow and Pyongyang must immediately provide military assistance by “all means” if either is attacked.

In exchange for thousands of North Korean soldiers, Russia has provided Pyongyang with anti-aircraft missiles and military equipment, according to South Korea’s national security adviser.

Shin Won-sik revealed on Friday during a broadcast on SBS TV that Russia has been supplying North Korea with advanced military technology to improve the regime’s defense capabilities, especially around Pyongyang.