Though staged to mark the anniversary of Japan's World War II defeat, the rally came just after Pyongyang said the South had committed an act of war by broadcasting anti-North propaganda across the border.
North and South Korea failed to agree on any joint celebration of the landmark anniversary of the liberation of their peninsula from Japan.
This year the North also suddenly announced that it was altering its time zone, moving it 30 minutes behind Japan's, to sweep away another legacy of Japan's colonization of the Koreas from 1910 to 1945. The time change went into effect amid bell-ringing and celebrations in Pyongyang after midnight Friday, though South Korea is sticking with the previous time zone.
While there were no incidents during the rally in the DMZ, North Korea has threatened to attack South Korean loudspeakers that are broadcasting anti-Pyongyang propaganda messages across their shared border, the world's most heavily armed.
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Seoul retaliated by restarting the loudspeaker propaganda broadcasts for the first time in 11 years.
North Korea's army said in a statement that the broadcasts are a declaration of war, and that if they are not immediately stopped "an all-out military action of justice" would ensue.
South Korean President Park Geun-hye urged Pyongyang to "wake up" from the delusion that it could maintain its government with provocation and threats.
Pyongyang's powerful National Defense Commission claimed Friday that Seoul fabricated the evidence and demanded video proof. The explosions resulted in one soldier losing both legs and another soldier one leg.