SEOUL, South Korea — President Park Geun-hye of South Korea on Saturday urged North Korea to stop what she called military provocations on the border, hours after the North threatened to attack loudspeakers that the South has begun using to blast propaganda messages into North Korea.

Ms. Park’s comments, in a speech on the 70th anniversary of the end of World War II and the liberation of the Korean Peninsula, then unified, from Japanese rule, came a week and a half after two South Korean soldiers were badly wounded by land mines that the South says were planted by the North in the demilitarized zone now dividing the Koreas.

“North Korea must wake up from its delusional belief that it can maintain its regime through provocations and threats,” Ms. Park said in her speech. “They lead only to isolation and destruction.”

South Korean leaders have traditionally commemorated the anniversary of the war’s end, called Liberation Day here, with a speech expressing hope for Korean reunification. The end of Japanese colonial rule seven decades ago was soon followed by Korea’s division, as the Soviet Union installed a communist government in the north and the United States a capitalist one in the south.