The Communist country opposes the drills, saying they are "an unpardonable infringement upon the sovereignty and dignity" of North Korea "as they evidently target [the North) which is in the mourning period," the official Korean Central News Agency reported.
The mourning reference was to North Korean leader Kim Jong Il, who died in December after being at the helm for 17 years. He was succeeded by his youngest son, Kim Jong Un, an enigmatic figure seen by Korean peninsula observers as trying to consolidate his power.
Referring to the drills, KCNA said they defy "strong domestic and foreign public protest and condemnation," adding "hundreds of thousands of troops are poised for a war, carrying nuclear war equipment."
"The army and people of [North Korea] are fully ready to fight a war with them," said KCNA, which began verbally lashing the United States and South Korea during the weekend.
"The warmongers will meet destruction in the fire kindled by them if they go reckless, misjudging the strong will of the Koreans to defend peace.
"The U.S. is the mastermind who worked out the war scenario against [North Korea] and has continuously staged the military drills in and around South Korea by egging its stooges."
South Korea's Yonhap News Agency said one set of drills that began Monday will last through March 9, involving about 200,000 South Korean and 2,100 U.S. troops. A second training exercise will run from March 1 to April 30.