Reuters--  The annual U.S.-South Korean drill, called Vigilant Ace, will run until Friday, with six F-22 Raptor stealth fighters to be deployed among the more than 230 aircraft taking part. The exercises have been condemned as a provocation by the isolated North.

F-35 fighters will also join the drill, which will also include the largest number of 5th generation fighters to take part, according to a South Korea-based U.S. Air Force spokesman.

Around 12,000 U.S. service members, including from the Marines and Navy, will join South Korean troops. Aircraft taking part will be flown from eight U.S. and South Korean military installations.

South Korean media reports said B-1B Lancer bombers could join the exercise this week. The U.S. Air Force spokesman could not confirm the reports.

The joint exercise is designed to enhance readiness and operational capability and to ensure peace and security on the Korean peninsula, the U.S. military had said before the drills began.

The drills come a week after North Korea said it had tested its most advanced intercontinental ballistic missile ever in defiance of international sanctions and condemnation.

Pyongyang warned at the weekend the Vigilant Ace exercise was pushing tensions on the Korean peninsula towards “a flare-up”, according to North Korean state media.