Ri told Tass that the North's nuclear weapons represent a deterrent to protect the country from the U.S.
The warplanes first conducted a simulated air-to-ground missile drill over the waters east of the Korean Peninsula and then flew over South Korea and conducted the same drill over the waters west of the peninsula, the South Korean military said.
"Although I will not comment on intelligence matters or specific incidents related to cyber intrusion, I can assure you that we are confident in the security of our operations plans and our ability to deal with any threat from North Korea", Pentagon spokesman Colonel Robert Manning told reporters.
Tass quoted North Korean Foreign Minister Ri Yong Ho on Wednesday accusing U.S. President Donald Trump of "setting a fuse of war" with his September speech at the United Nations.
"I made the decision. because I felt that the presence will be inconsistent with Australia's stated aim of placing maximum diplomatic and economic pressure on North Korea", Bishop said.
Ri also said that North Korea's nuclear programme was the "precious fruition of the Korean people's bloody struggle for defending the destiny and sovereignty of the country from the protracted nuclear threat of the U.S. imperialists and a treasured sword of justice".
Visits by US warships and bombers along with regular joint exercises with the South infuriate North Korea, which considers them a sign of aggression and a rehearsal for an invasion.
He added that North Korea would not rule out "the use of the most extreme measures in response".
Trump hosted a discussion on Tuesday on options to respond to any North Korean aggression or, if necessary, to prevent Pyongyang from threatening the United States and its allies with nuclear weapons, the White House said in a statement.
Two bombers operating out of Andersen Air Force Base in Guam carried out the drills, US Pacific Air Forces said in a statement.
Lee, who didn't specify his sources, said the plans allegedly stolen by the North include operations for tracking the movement of the North's leadership, isolating their hideouts, executing air assaults and follow-up actions for securing and eliminating targets, which would obviously include North Korean leader Kim Jong Un.
China, North Korea's main ally and trading partner, has consistently argued sanctions alone will not work, urging Washington and Pyongyang to lower their rhetoric and return to the negotiating table.
This is the second time since Trump's fiery U.N. General Assembly speech that North Korea vocally accused the US of declaring war on its country.
USA defense officials have told CNN that the aircraft carrier USS Ronald Reagan will conduct scheduled exercises with the South Korean navy off the peninsula at the end of this month.