North Korean threats to deliver “preventive nuclear strikes” could create a legal basis for the use of military force against the country, Russia’s Foreign Ministry warned on Monday.

The Russian statement, which follows a North Korean response to the largest joint U.S.-South Korea military drills to ever occur on the peninsula, underscores growing concern about developments between the two Koreas.

“We consider it to be absolutely impermissible to make public statements containing threats to deliver some ‘preventive nuclear strikes’ against opponents,” a translation of the Russian Foreign Ministry response to North Korea’s threats said on Monday.

“Pyongyang should be aware of the fact that in this way