The three missiles launched on Tuesday were a dry run for attacks on South Korean ports and airfields hosting United States military "hardware", the North's official KCNA news agency said.
North Korea is testing nuclear detonators for strikes against the South - in yet another defiant gesture from despot Kim Jong un.
The U.S., South Korea and Japan, which have moved to strengthen their trilateral relationship in recent months, strongly denounced the missile launches, saying they violate U.N. Security Council resolutions banning the North from using ballistic-missile technology. Seoul officials said all three missiles landed in the waters off the North's east coast.
North Korea conducted its fourth nuclear test in January, and held a launch of a spacecraft many suspected was actually a missile test in February.
The decision has also been controversial in South Korea, particularly in the rural area of Seongju, about 130 miles southeast of Seoul, which has been chosen as the site for the battery.
The three reported launches came as North Korea criticised the planned deployment of an advanced U.S. missile defence system in South Korea.
The media also clearly stated that the North will not stop its development of their ballistic missiles, a practice recently criticized by the South Korean President as "acts of threatening the peace of worldwide society", during a recent Asia-Europe Meeting (ASEM).
In this photo, taken in Guam on July 19, 2016, U.S. Congresswoman Madeleine Bordallo talks with South Korean reporters about the THAAD system on the island.
North Korea says it will not give up on its nuclear deterrence unless Washington ends its hostile policy toward Pyongyang and dissolves the US-led United Nations command in South Korea.
It is unclear whether North Korea actually has the technology that it boasts about having.
The two Koreas remain technically at war since their 1950-53 conflict ended with an armistice instead of a peace treaty.
"We know how valuable THAAD is on Guam and this deployment will complement the battery permanently stationed on our island", Bordallo said, upon the disclosure by USA and South Korean officials.
Although South Korea approved the planned deployment of the U.S. Terminal High-Altitude Area Defense (THAAD) systems in the Republic of korea, Seoul insists the system will operate autonomously and independently of the U.S. regional missile defense system. He made clear that the THAAD to be employed in South Korea will not be sharing information with the wider MD network.
China opposes the deployment plan, which it believes will significantly strengthen the U.S.' already strong presence on the Korean Peninsula.