"In the current serious situation in the country, all soldiers of the Korean People's Army (KPA) have to maintain full combat readiness," the KPA command said as quoted by the Korean Central News Agency.
Pyongyang considers the plans by Seoul and Washington to conduct military exercises preparation for an attack. The U.S. and South Korea say the exercises, which are held annually, are purely defensive.
The exercises, codenamed Key Resolve/Foal Eagle, will be conducted in South Korea. They will involve 26,000 U.S. servicemen and a U.S. aircraft carrier. The number of South Korean soldiers has not been announced.
South and North Koreas are formally in a state of war, as the 1950-1953 conflict on the Korean Peninsula ended only in a truce agreement, not in a peace treaty.