A test launch of a Hwasong-10, a ground-to-ground intermediate-range ballistic missile, in an undated photo released by the state-run Korean Central News Agency on June 23, 2016. KCNA via Reuters

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.

"They want to know if they can get these missiles out into the field rapidly and deploy them all at once," Lewis told The Post. "They are practicing launching a nuclear-armed missile and hitting targets in Japan as if this was a real war."

The extended-range Scud missiles could be produced more cheaply than other medium-range missiles in the Hermit Kingdom’s arsenal, according to Lewis. This could be disastrous for allied nations, such as Japan and South Korea, not only because North Korea could release a barrage of these missiles, but the rate at which they could be fired can be difficult to counter, even with the US's defensive systems.

One of these defensive systems, the antimissile battery system, known as the Terminal High Altitude Area Defense (THAAD), was in the process of being deployed on Monday night in Osan Air Base, less than 300 miles from the missile launch location.

"Continued provocative actions by North Korea, to include yesterday's launch of multiple missiles, only confirm the prudence of our alliance decision last year to deploy THAAD to South Korea," said Adm. Harry Harris, commander of US Pacific Command, in a news release.

Designed to shoot incoming missiles, THAAD has been compared to shooting a bullet with another bullet. However, analysts say that the system would have difficulty in intercepting missiles launched simultaneously — as in Monday’s test.

According to a KCNA statement translated by KCNA Watch, Kim Jong Un, the leader of North Korea, supervised the launches from the Hwasong artillery units, who are "tasked to strike the bases of the U.S. imperialist aggressor forces in Japan in contingency."

The launches came shortly after an annual series of US-South Korea military exercises that kicked off earlier this month. The ground, air, naval, and special-operations exercises, which consist of 17,000 US troops and THAAD systems, was predicted by scholars to be met with some retaliatory measures by North Korea.

"In spite of the repeated warnings from [North Korea], the United States kicked off this month the largest-ever joint military exercise with South Korea,” said North Korean diplomat Ju Yong Choi during a UN-sponsored conference in Geneva on Tuesday, according to Reuters. "The annual, joint military exercise is a typical expression of US hostile policy towards the DPRK, and a major cause of escalation of the tension, that might turn into actual war."