Seoul’s foreign ministry has expressed “grave concern” after Russia’s lower house of parliament ratified the country’s comprehensive strategic partnership treaty with North Korea. 

A foreign ministry official made the announcement Friday amid intelligence reports that North Korea has deployed troops to Russia. 

The official said the Seoul government strongly urges Pyongyang to immediately withdraw its troops and halt its unlawful cooperation with Moscow.

The government also stressed that it will take corresponding measures decisively in cooperation with the international community.

On Thursday the State Duma, the lower house of Russia’s Federal Assembly, ratified the comprehensive strategic partnership treaty that Russia signed with North Korea in June.

The upper house is expected to ratify it soon.