SEOUL, South Korea — South Korea’s spy agency said Friday that North Korea has dispatched troops to support Russia’s war against Ukraine, a development that could bring a third country into the war and intensify a standoff between North Korea and the West.

The National Intelligence Service said in a statement that Russian navy ships transferred 1,500 North Korean special operation forces to the Russian port city of Vladivostok from Oct. 8 to Oct. 13. It said more North Korean troops are expected to be sent to Russia soon.

The North Korean soldiers deployed in Russia have been given Russian military uniforms, weapons and forged identification documents, the NIS said. It said they are currently staying at military bases in Vladivostok and other Russian sites such as Ussuriysk, Khabarovsk and Blagoveshchensk, and that they will likely be deployed to battle grounds after completing their adaptation training.

The NIS posted on its website satellite and other photos showing what it calls Russian navy ship movements near a North Korean port and suspected North Korean mass gatherings in Ussuriysk and Khabarovsk in the past week.

South Korean media, citing the NIS, reported that North Korea has decided to dispatch a total of 12,000 troops formed into four brigades to Russia. The NIS did not immediately confirm the reports.

If confirmed, it would be North Korea’s first major participation in a foreign war. North Korea has 1.2 million troops, one of the largest militaries in the world, but it lacks actual combat experience.

Many experts question how much the North Korean troop dispatch would help Russia, citing North Korea’s outdated equipment and shortage of battle experience.

Experts also said that North Korea likely received Russian promises to provide security support over the intense confrontations over its advancing nuclear program with the U.S. and South Korea.

During a meeting in Pyongyang in June, North Korean leader Kim Jong Un and Russian President Vladimir Putin signed a pact stipulating mutual military assistance if either country is attacked, in what was considered the two countries’ biggest defense deal since the end of the Cold War.

South Korea’s presidential office said in a statement that President Yoon Suk Yeol had presided over an emergency meeting earlier Friday to discuss North Korea’s troop dispatch to Russia. The statement said participants of the meeting agreed that North Korea’s troop dispatch poses a grave security threat to South Korea and the international community.

But the presidential office gave no further details like when and how many North Korean soldiers have been sent to Ukraine and what roles they are expected to play.