SEOUL, South Korea (AFP) — North Korea has ratified a landmark defense pact with Russia, state media reported Tuesday, sealing a deepening security cooperation between the two nations amid Moscow’s war in Ukraine.

The deal “was ratified as a decree” of Kim Jong Un, the Korean Central News Agency (KCNA) said, referring to the leader by his title of “President of the State Affairs of the Democratic People’s Republic of Korea.”

The notice comes after Russian lawmakers voted unanimously last week to ratify the deal, which President Vladimir Putin later signed.

“The treaty will take effect from the day when both sides exchanged the ratification instruments,” KCNA said.

North Korea has become one of the most vocal and important backers of Russia’s full-scale offensive on Ukraine.

Pyongyang has long been accused by Western nations of supplying Moscow with artillery shells and missiles for use in Ukraine, but that support has escalated in recent weeks with the reported arrival of thousands of North Korean troops prepared to engage in combat.

Putin and Kim signed the strategic partnership treaty in June, during the Kremlin chief’s visit to Pyongyang. It obligates both states to provide military assistance “without delay” in the case of an attack on the other and to cooperate internationally to oppose Western sanctions.

Putin hailed the deal in June as a “breakthrough document.”

North Korea’s Foreign Minister Choe Son Hui recently visited Moscow and said her country would “stand firmly by our Russian comrades until victory day.”

She called Moscow’s offensive against Ukraine a “sacred struggle” and said Pyongyang believed in Putin’s “wise leadership.”

Citing intelligence reports, South Korea, Ukraine and the West say North Korea has deployed around 10,000 troops to Russia to fight against Ukraine.

When asked publicly about the deployment last month, Putin did not deny it, instead deflecting the question to criticize the West’s support of Ukraine.

In exchange for sending troops, the West fears Russia is offering North Korea technological support that could advance Pyongyang’s nuclear weapons program.