North Korea’s state-run media announced its latest missile launches were conducted to practice hitting US military bases in Japan, according to The Washington Post on Tuesday.

“If the United States or South Korea fires even a single flame inside North Korean territory, we will demolish the origin of the invasion and provocation with a nuclear tipped missile,” a Korean Central News Agency statement read.

Three of the four ballistic missiles fired Monday morning flew 600 miles and landed in the sea in Japan’s exclusive economic zone. The other missile landed outside the zone.

Studying the photos provided by North Korea, analysts at the Middlebury Institute of International Studies deduced that the missiles were extended-range Scuds. Having tested these missiles in the past, Jeffrey Lewis, director of the East Asia Nonproliferation Program at the Middlebury Institute, said that North Korea’s test was not to see whether they could operate but to assess how fast units could deploy them.