SEOUL, South Korea (AP) — North Korea said Thursday its latest missile launches simulated “scorched earth” nuclear strikes on South Korea and that it’s also been rehearsing an occupation of its rival's territory in the event of conflict.

Pyongyang has previously tested nuclear-capable missiles and described how it would use them in potential wars with South Korea and the U.S. But the North’s disclosure of detailed war plans reaffirmed its aggressive nuclear doctrine to intimidate its opponents, as it escalates its protest of the ongoing South Korean-U.S. military exercises that it views as a major security threat, observers say.

North Korea’s military said it fired two tactical ballistic missiles from the capital on Wednesday night to practice “scorched earth strikes” at major command centers and operational airfields in South Korea, according to the official Korean Central News Agency.

The North’s military said the missiles carried out their simulated strikes through air bursts, suggesting it confirmed the explosions of dummy warheads at a set altitude.

North Korea said its missile tests were response to the United States’ flyover of long-range B-1B bombers for a joint aerial training with South Korea earlier Wednesday as part of the allies’ field exercises.

“(The aerial drill) is a serious threat to (North Korea) as it was just pursuant to the scenario for a preemptive nuclear strike at” North Korea, the Korean People’s Army general staff said. “The KPA will never overlook the rash acts of the U.S. forces and the (South Korean) military gangsters.”

The missile launches Wednesday were the latest in the North’s barrage of weapons tests since last year.

According to South Korean and Japanese assessments, the two short-range missiles travelled a distance of 360-400 kilometers (225-250 miles) at the maximum altitude of 50 kilometers (30 miles) before landing in the waters between the Korean Peninsula and Japan.

South Korea’s Joint Chiefs of Staff called the launches “a grave provocation” that threatens international peace and violates U.N. Security Council resolutions that ban any ballistic launches by North Korea. The U.S. Indo-Pacific Command said the U.S. commitment to the defense of South Korea and Japan remains “ironclad.”

South Korean and Japanese authorities said their warplanes conducted combined aerial drills with U.S. B-1B bombers respectively on Wednesday. South Korea’s Defense Ministry said that Wednesday’s B-1B deployment is the 10th flyover by U.S. bombers on the Korean Peninsula this year.

North Korea is extremely sensitive to the deployment of U.S. B-1B bombers, which can carry a huge number of conventional weapons. The North describes the bombers as “nuclear strategic” although the planes were switched to conventional weaponry in the 1990s.

On Aug. 21, the U.S. and South Korean militaries kicked off their summer Ulchi Freedom Shield computer-simulated command post exercise. During this year’s training, slated to end later Thursday, the allies have included more than 30 kinds of field exercises, such as Wednesday’s joint aerial exercise involving the B-1B aircraft.

North Korea calls major U.S.-involved military drills on and near the Korean Peninsula preparation for invasion. Washington and Seoul officials maintain their drills are defensive. The U.S. stations about 28,000 troops in South Korea.

KCNA said Kim on Tuesday visited an army post where his military has been holding command post drills in response to the South Korean-U.S. military training. It said the drills are aimed at practicing procedures for “occupying the whole territory of the southern half” of the Korean Peninsula in the event of war.

Kim underscored the need to “deal a heavy blow at the enemy’s war potential and war command center and blinding their means of command communication at the initial stage of operation.” Kim also detailed tasks to acquire an ability to launch “simultaneous super-intense strikes” at key enemy military targets and other sites whose destruction can cause social and economic chaos, according to KNCA.

The North’s report showed it has operational plans to launch full-blown attacks on South Korea in the event of military clashes between the rivals to achieve Korean unification by force, said analyst Cheong Seong-Chang at the private Sejong Institute in South Korea. He said that North Korea plots to conduct nuclear and EMP (electromagnetic pulse) attacks at the early stage of war.

South Korea’s Unification Ministry said later Thursday it strongly condemns North Korea for openly revealing its intent to attack the South. It warned North Korea will only face “an overwhelming response” by South Korea, the U.S. and Japan if it continues its provocation and military threats.

The ministry said it was North Korean state media’s first report on command post drills involving the whole military since Kim took power in late 2011.

North Korea has openly threatened to use its nuclear weapons first in potential conflicts with South Korea and the U.S. since it last year adopted a new law that authorized the preemptive use of nuclear weapons in a broad range of situations.

Kim has been pushing hard to expand and modernize his weapons arsenals. Its second attempt at launching a spy satellite failed last week, but it plans a third attempt in October.

Foreign experts say Kim eventually wants to use his enlarged weapons arsenals to force the U.S. to make concessions when diplomacy resumes.