"Sunday morning, the 21st, [authorities] spotted two suspected cruise missiles in the Onchon, South Pyongan area," the JCS said, adding that Seoul was aware of the test and monitoring in real-time, but it's their decision not to disclose all information related to North Korea.
News of the mysterious test over the weekend was first reported by The Washington Post and later confirmed to ABC News on Tuesday.
The Washington Post was first to report that the launches had taken place.
Curiously, neither North Korea nor South Korea had acknowledged the firing of the two missiles immediately on Sunday as is routinely done by both countries. North Korea typically discloses launches to promote its technological advances, while South Korea provides quick updates to highlight their provocative nature.
FROM MARCH 2020: North Korea fires weapons after threatening 'momentous' action
This weekend's launches are the first to occur during the Biden administration, which has acknowledged reaching out to Kim Jong Un's regime.
Senior Biden administration officials downplayed the test as "normal activity" that was on the low end of the spectrum of provocations from North Korea.
"We see this action in the category of normal activity," a senior administration official told reporters.
"North Korea has a familiar menu of provocations when it wants to send a message to a U.S. administration," said the official, who listed ballistic missiles fired from mobile launchers and submarines, as well as nuclear and thermonuclear tests as falling into that category.
"Experts rightly recognized what took place last weekend as falling on the low end of that spectrum," said the official.
"I would say generally speaking, what we saw this weekend, does not fall in that category," one official said.
The officials indicated that North Korea has still not responded to the administration's outreach and did not see the weekend's "activity" as "closing the door" on a potential response in the future.
Experts in Seoul agreed that the missile launch was a message to the U.S. ahead of the Biden administration's new North Korea policy review expected in the coming weeks.
"North Korea is adjusting its level of message towards the U.S. by not reporting its weapons tests success through the state media, " Cha Du Hyeogn, visiting research fellow at Asan Institute of Policy Studies, told ABC News. "Instead of launching middle to long-range missiles which will bump against the UN Security Council resolutions, North Korea chose to fire short-range missiles just enough to show off their improving military capabilities."
North Korea had recently complained publicly about a new round of American and South Korean military exercises taking place in South Korea.
Through North Korean state media, Kim's politically influential sister Kim Jo Yong warned the Biden administration that if it wanted "to sleep in peace" for the next four years, "it had better refrain from causing a stink at its first step."
"They have no reason to mess up the future of US-DPRK relations at the moment. So we could say that it's North Korea's wait-and-see tactic by expressing discontent in a lightly controlled manner," Yang Uk, professor of National Defense Strategy at Seoul based Hannam University, told ABC News.
Ahead of Defense Secretary Lloyd Austin's visit to South Korea last week, U.S. officials had expressed concerns that North Korea may have been preparing to fire missiles in response to his visit. However, this weekend's two missile launches took place days after Austin had left South Korea.
Since the 2018 hand-shake agreement that former President Donald Trump reached with Kim, North Korea has not conducted any long-range missile tests. As North Korea resumed testing shorter-range ballistic missiles after that agreement, the Trump administration said they did not violate the spirit of the agreement.
However, it is believed that in that time, North Korea has progressed with its Intercontinental Ballistic Missile (ICBM) technology, unveiling a new, large, mobile-launched ICBM in a military parade last October.
"The Kim Jong Un regime has achieved alarming success in its quest to demonstrate the capability to threaten the U.S. homeland with nuclear-armed ICBMs, believing such weapons are necessary to deter U.S. military action and ensure his regime's survival, Gen. Glen VanHerck, the commander of U.S. Northern Command, told Congress last week in written testimony.
VanHerck described North Korea's new ICBM as further increasing the risk posed to the United States.
"The North Korean regime has also indicated that it is no longer bound by the unilateral nuclear and ICBM testing moratorium announced in 2018, suggesting that Kim may begin flight testing an improved ICBM design in the near future," said VanHerck.