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 missiles came from the Hwangju region, South Korea's Joint Chiefs of Staff said.
However on Tuesday South Korea said the North fired three ballistic missiles from inland that flew about 310 to 375 miles before crashing into the sea.
(Stand-up) "According to Seoul's Foreign Ministry on Tuesday, South Korea is doing everything it can on the diplomatic front to ensure a stronger statement on North Korea, which is expected to be issued at the ASEAN Regional Forum in Laos this month".
North Korea's state radio has recently broadcast strings of indecipherable numbers in a possible move echoing a Cold War-era method of sending coded messages to spies operating in South Korea.
The tests were monitored by Kim Jong-Un and the range of the missiles was limited to simulate preemptive attacks on South Korean ports and airfields hosting USA military "hardware", the North's official KCNA news agency said.
Choi Kang, a researcher at the Asan Institute for Policy Studies, said, "If the THAAD battery is useless against North Korea's missile threat, the North would have no reason to react so sensitively".
Pyongyang fired what is thought to be two short-range Scuds and the third medium-range Rodong missile on Tuesday (19 July), which, again, escalated tensions in the Korean peninsula.
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).
North Korean leader Kim Jong Un was accompanied at the launch by top officials of the military and arms industry, including Kim Rak Gyom, commander of the KPA Strategic Force.
Another military source that the SCUD missiles would likely be Pyongyang's weapon of choice if it were to target places like Seongju, where the THAAD system will be deployed.
Since carrying out a fourth nuclear test in January, which prompted a significant tightening of United Nations sanctions, North Korea has claimed a series of technical breakthroughs for its weapons programme.
Shin also said analysis of North Korea's cyberterror networks shows there are at least three organizations in operation.
Last week, USA and South Korean officials announced the deployment of the THAAD system to South Korea.
"What matters is how we enforce those sanctions and that actually involves better coordination among all the countries in the region and that includes China", Mark Toner, a spokesman for the U.S. State Department, told The Korea Times.
'I can't speak to their intentions, but we hope that the North will refrain from an old practice like this and behave in a manner that's conducive to improving South-North ties, ' Jeong said.