South Korea and the US wrapped up this year's Foal Eagle exercise earlier in the day, with the Key Resolve command post drill having concluded last month.
This year's exercises were the biggest of their kinds, having come on the heels of the North's nuclear test in January and a long-range rocket launch in February.
This year's Key Resolve and Foal Eagle drills were "the worst-ever military provocations that pushed the situation on the Korean Peninsula to the brink of a nuclear war," the North's Korean Central News Agency quoted a foreign ministry spokesman as saying.
The spokesman added that the two-month-long exercises were "tantamount to an open declaration of war" and "undisguisedly revealed the US attempt to mount a preemptive attack" on North Korea.
The two exercises brought together some 300,000 South Korean armed forces and 17,000 US forces.
North Korea launched a string of short- to mid-range missile launches during the course of the two-month exercise, including the firing of two Musudan intermediate-range ballistic missiles on Thursday.
YNA/MNA