Tens of thousands of South Korean and US troops Monday began a military exercise simulating an all-out North Korean attack, as Pyongyang matched Seoul in resuming a loudspeaker propaganda campaign across their heavily fortified border.
The annual Ulchi Freedom exercise, which will run through August 28, is largely computer-simulated but still involves 50,000 Korean and 30,000 US soldiers.
The drill plays out a full-scale invasion scenario by nuclear-armed North Korea and both Seoul and Washington insist it remains purely defensive in nature.
Pyongyang views Ulchi Freedom as willfully provocative and has threatened the "strongest military counteraction" should this year's exercise go ahead.
"Such large-scale joint military exercises ... are little short of a declaration of a war," the North's Committee for the Peaceful Reunification of Korea, which oversees cross-border issues, said last week.
The committee specifically warned of the drill's potential for an accidental military clash that could trigger an "all-out" conflict.
Military tensions are already running high along the Korean peninsula after South Korea blamed the North for landmine blasts that maimed members of a border patrol earlier this month.
The South retaliated by resuming high-decibel propaganda broadcasts across the border, using loudspeakers that had lain silent for more than a decade.
North Korea has denied any involvement in the mine blasts and threatened "indiscriminate" strikes against South Korean border units unless the broadcasts were halted immediately.
But on Monday Seoul's defense ministry reported that Pyongyang had resumed its own loudspeaker propaganda campaign at a site on the eastern section of the border.
The two Koreas had blasted propaganda messages at each other for years before the practice was discontinued by mutual agreement in 2004 during a period of rapprochement.
