After Thursday's missile launches, North Korea announced it would "liquidate" South Korean assets left behind in the Kaesong industrial zone and in the Mount Kumgang tourist zone
North Korea fired two short-range ballistic missiles into the sea on Thursday in defiance of UN Security Council resolutions, as South Korean and U.S. forces conducted massive war games.
The North also announced it had scrapped all agreements with the South on commercial exchange projects and would "liquidate" South Korean assets left behind in its territory.
North Korea has a large stockpile of short-range missiles and is developing long-range and intercontinental missiles as well. Thursday's missiles flew about 500 km (300 miles) into the sea off the east coast city of Wonsan and probably were part of the Soviet-developed Scud series, South Korea's defence ministry said.
Japan, which is within range of the longer-range variant of Scud missiles or the upgraded Rodong missiles, lodged a protest through the North Korean embassy in Beijing, Japan's Kyodo news agency reported.
North Korea often fires short-range missiles when tensions rise on the Korean peninsula. Pyongyang gets particularly upset about the annual U.S.-South Korea drills, which it says are preparations for an invasion.
The U.S. and South Korea remain technically at war with the North because the 1950-53 Korean War ended in an armed truce instead of a peace agreement.
Around 17,000 U.S. military personnel are participating alongside some 300,000 South Korean troops in what South Korea's Defence Ministry has called the "largest-ever" joint military exercises.
North Korea on Sunday warned it would make a "pre-emptive and offensive nuclear strike" in response to the exercises.