South Korean lawmaker Park Sun-won said, after a briefing by his country’s National Intelligence Service, that 1,500 more troops from the rival North had gone to Russia, taking the total deployment to 3,000.

“The planned deployment of about 10,000 troops from North Korea to Russia is expected to have occurred by December,” added Park, who sits on the national assembly intelligence committee.

Neither Russia nor North Korea’s state media have commented since Seoul’s spy agency said last week said Pyongyang had decided to send a “large-scale” troop deployment to Russia to fight Ukraine. But international concerns are mounting. Germany said Wednesday it had summoned North Korea’s envoy over Pyongyang’s support to Russia in Ukraine and warned the reclusive state against sending troops.

“We address fighters of the Korean People’s Army who were sent to help Putin’s regime. You must not die senselessly in a foreign land,” said a statement issued by an initiative run by Kyiv’s military intelligence.

Another lawmaker, Lee Seong-Kweun, said rumours were spreading within the tightly-controlled North that the elite “Storm Corps” had been sent to Russia. “In response, North Korean authorities are said to be strictly controlling information, and there are indications that they are relocating and isolating the families of the deployed soldiers in undisclosed locations to better manage and control them.”

As a result, Russian instructors expect “there could be a significant number of casualties if North Korean forces are deployed to the frontlines,” Lee added.

Experts have said that in return for the troops, North Korea is likely aiming to acquire military technology, ranging from surveillance satellites to submarines, plus possible security guarantees from Moscow.