As part of the exercise, two American B-1 bombers and South Korean and Japanese fighter jets flew over the Korean Peninsula.
U.S. 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. Pyongyang has historically conducted tests on noteworthy anniversaries and holidays such as a missile test on July 4 for America's Independence Day.
"Thus far, the suspected North Korean actions are consistent with a desire to demonstrate a deterrent capability rather than a prelude to an unprovoked first-strike in cyberspace; however, North Korea linked actors are bold, have launched multiple cyber attacks created to demonstrate national strength and resolve, and have little concern for potential discovery and attribution of their operations", FireEye researchers said in a blog.
"While I would not characterize them as the best in the world, they are among the best in the world and the best organized", Army Gen. Vincent Brooks, commander of U.S. Forces Korea, told the Senate past year.More news: Heavy Smoke, Ash From Anaheim Fire Causes Unhealthy Air Quality Across Region
More news: Sadio Mané Faces Six-Week Layoff Following Hamstring Injury
More news: Top 5 Jaw-Dropping Moments From "Star Wars"
Meanwhile, China - North Korea's closest ally and trading partner - expressed alarm at how far the rhetoric on both sides had gone, warning of the increased risk of a "fatal misjudgement"."The global community won't accept North Korea as a nuclear power".
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.
Russia's TASS news agency quoted North Korean Foreign Minister Ri Yong Ho as saying: "With his bellicose and insane statement at the United Nations, Trump, you can say, has lit the wick of a war against us".
Despite the global sanctions, North Korean leader Kim Jong-un continues to develop nuclear weapons and advance his nation's ballistic missile program.
Information on South Korea's special forces was also reportedly accessed, as well as important details on significant power plants and military facilities in the South.