South Korea has announced a series of heavy-weaponry, live-fire military drills with the US as a response to a recent landmine attack blamed on North Korea.
Four exercises, involving tanks, howitzer guns, attack helicopters and fighter bombers, will be held in coming weeks in an area around 30km south of the North Korean border, the defence ministry said.
"This will show our preparedness to retaliate against any provocative acts, including such treacherous acts of aggression as the landmine attack," a ministry spokesman said.
The first drill was to take place late on Wednesday, with the last one conducted towards the end of the month.
Speaking at an official function at her Blue House residence, President Park Geun-Hye reiterated that South Korea would "deal strongly" with any North Korean provocation.
The live-fire drills will be separate from the full-scale, annual "Ulchi Freedom" joint exercise that kicks off next Monday and lasts for two weeks.
The annual drills always trigger a surge in military tensions with the nuclear-armed North which has repeatedly condemned them as rehearsals for invasion.
South Korea has vowed the North will pay a "harsh price" for the mine blasts that maimed two of its soldiers during a border patrol last week.
The military said investigations showed North Korean soldiers had sneaked across the border to plant the mines along a known patrol route.
Pyongyang has yet to respond to the charge.
South Korea has ramped up border security in the wake of the blasts and - after a break of more than a decade - resumed its broadcast of propaganda messages into the North, using batteries of powerful loudspeakers along the border.
The loudspeakers had broadcast messages extolling the virtues of South Korea for years before the practice was discontinued by mutual agreement in 2004 during a period of rapprochement between the two Koreas.
Briefing parliament on Wednesday, Han Min-Koo, South Korea's defence minister, said the loudspeakers were now operating at four out of a possible 11 sites.
"We intend to expand the broadcasts to the fullest extent," the Yonhap news agency quoted Han as saying.