South Korea has expressed “serious concern” and condemned a new treaty between Russia and North Korea pledging “mutual assistance” against enemy attacks, warning that it could consider sending arms to Ukraine to counter the two countries’ growing military cooperation.

Hours after a National Security Council (NSC) meeting on Thursday, Seoul’s National Security Director Chang Ho-jin said in a statement released by the presidential office that the new Treaty on Comprehensive Strategic Partnership approaches the level of a formal alliance, even if it does not assure automatic military intervention.