South Korea believes the North has sent troops to Russia to support its war in Ukraine.

The National Intelligence Service said Friday an initial contingent of 1,500 special forces soldiers has already been deployed to Russia's Vladivostok.

The spy agency said it had "detected from the 8th to the 13th, North Korea transported its special forces to Russia via a Russian Navy transport ship, confirming the start of North Korea's military participation."

Separately, Yonhap news agency reported that Seoul's spy agency said the North had "recently decided to send four brigades of 12,000 soldiers, including special forces, to the war in Ukraine."

What do we know about the troops?

On Friday, South Korean President Yoon Suk Yeol held an unscheduled security meeting with key intelligence, military, and national security officials.

Yoon's office said the North has gone "beyond the transfer of military supplies to actual troop deployments."

It poses "a significant security threat not only to our country but also to the international community."

The country's spy agency reported that North Korean soldiers have been given Russian uniforms, weapons, and forged IDs. 

They are accommodated at military bases in Vladivostok, Ussuriysk, Khabarovsk, and Blagoveshchensk and will likely be deployed after training. 

The agency released satellite images showing Russian navy movements near a North Korean port and suspected North Korean gatherings in Ussuriysk and Khabarovsk.

Zelenskyy says some North Korean soldiers deployed in Ukraine

Russia had previously denied using North Korean troops in the war.

Kremlin spokesperson Dmitry Peskov described the claims as "another piece of fake news" during a news conference last week, according to Russian media.

Ukraine, however, says that some North Korean officers are already on the ground in Russian-occupied parts of Ukraine.

"From our intelligence we've got information that North Korea sent tactical personnel and officers to Ukraine," President Volodymyr Zelenskyy told reporters at the NATO headquarters on Thursday.

"They are preparing on their land 10,000 soldiers," he added. 

lo/wmr (AP, AFP, Reuters)