BEIJING (Kyodo) -- North Korea has ratified its defense cooperation treaty with Russia, state-run media reported Tuesday, amid allegations Pyongyang has sent a significant number of troops to support Moscow's invasion of Ukraine.

The Comprehensive Strategic Partnership treaty, which includes a provision for mutual assistance if either country comes under attack, was signed in June by North Korean leader Kim Jong Un and Russian President Vladimir Putin.

"The treaty will take effect from the day when both sides exchanged the ratification instruments," the Korean Central News Agency said, adding Kim signed a decree to ratify the treaty on Monday.

Russia, which launched a full-scale invasion of Ukraine in February 2022, has already ratified the treaty, sparking concern that the dynamics of the war could shift if North Korea accelerates its military support.

The pact stipulates, "In case any one of the two sides is put in a state of war by an armed invasion from an individual state or several states, the other side shall provide military and other assistance with all means in its possession without delay," KCNA reported in June.

It effectively revives the countries' mutual defense obligation under a 1961 accord that became invalid following the Soviet Union's collapse in 1991.

The treaty, which will be in "indefinite effect," covers bilateral cooperation on trade, the economy, energy and technology, and other areas, KCNA said.