Russia's state-run news agency says President Vladimir Putin has signed legislation to ratify a bilateral treaty with North Korea, which includes a promise of mutual military assistance if either country is attacked.

Tass and other media on Saturday reported Putin's signing of the law on ratification of the comprehensive strategic partnership treaty between Moscow and Pyongyang.

Putin signed the deal with North Korean leader Kim Jong Un during his visit to North Korea in June. The lower and upper houses of the Russian parliament had earlier approved the bill for ratification.

The treaty stipulates that if either of the parties is invaded and placed under a state of war, the other will deploy all means in its possession to provide military and other assistance, without delay.

The ratification procedure by the Russian side has now been completed with Putin's signing of the law. Observers are waiting to see how much military cooperation between Russia and North Korea will deepen based on the treaty as Moscow continues its invasion of Ukraine.