South Korea's military on Monday issued a surprisingly high figure regarding North Koreans killed or wounded fighting for Russia in the Ukraine war.

Seoul's Joint Chiefs of Staff announced its assessment that more than 1,000 have been killed or wounded since entering the conflict theatre. "Through various sources of information and intelligence, we assess that North Korean troops who have recently engaged in combat with Ukrainian forces have suffered around 1,100 casualties," the official statement said.

"We are particularly interested in the possibility of additional deployments" of North Korean soldiers in support of Russia's war effort, it continued. South Korea's military stressed its belief that Pyongyang is "preparing for the rotation or additional deployment of soldiers."

The majority of the 1,100 casualties figure is said to involve troops being wounded and injured, given that last week Seoul's spy agency told lawmakers it assesses that at least 100 North Korean soldiers have been killed.

They first reportedly entered combat in December, and appear concentrated in Russia's Kursk region, which suffered a cross-border offensive by Ukrainian troops last August. The North Koreans have reportedly been helping their Russian ally regain its own territory.

There's as yet been little to no evidence that North Koreans are actually fighting inside Ukraine, in the Donbas front line region for example.

But Western intelligence has estimated that some 10,000 DPRK troops were sent to Russia. The White House and NATO officials have called attacks on these foreign troops legitimate and said they are "fair game". 

The NY Times has newly speculated as to why these forces are taking such heavy casualties: 

The troops that North Korea deployed are from its “​Storm” Corps​, special forces that are among the military’s best trained ​and most heavily indoctrinated. But they were badly prepared for​ drone attacks and the unfamiliar terrain far from their isolated homeland, according to South Korea’s National Intelligence Service.

More than 100 of them were killed and 1,000 others wounded in their first battles, the intelligence agency told South Korean lawmakers in a briefing on Thursday. The agency said a general-ranking officer may be among those killed, according to Lee Seong-kweun, a lawmaker who spoke to reporters after the closed-door briefing.

Already, Pyongyang has long faced accusations that it is shipping weapons, and especially artillery shells, to Russian forces for use in Ukraine.

Kiev has spoken of an 'axis' which is at war against Ukraine, including Russian, Iran, and now North Korea. South Korea's military has also of late accused the Kim Jong Un regime of sending suicide drones to Russia to bolster Putin's UAV arsenal.

The Kremlin has defended the presence of foreign partner forces in Russia, helping to regain territory in the south, given this past summer Putin and Kim signed a military and security treaty. The treaty included agreements for each to assist if the other's sovereign territory comes under attack.