Two projectiles launched by North Korea on Thursday were "presumed to be fired from a super-large caliber multiple rocket launcher," South Korean army officials said.
"This North Korean action does not aid the easing of tension on the Korean Peninsula," said Army Major Gen. Jeong Dong-jin of the South Korean Joint Chief of Staff.
"We express a strong regret and again call for immediate suspension of actions that heightens tension," he added.
Jeong said the two short-range projectiles, fired at 4:59 p.m. local time, had a maximum flight distance of about 380 kilometers (236 miles) and an altitude of 97 kilometers (60 miles).
Japan's Prime Minister Shinzo Abe said his country had not confirmed that the missiles landed in Japan's marine zone, the area officially known as the Japanese Exclusive Economic Zone.
"But the multiple ballistic missiles launched by North Korea are a serious threat to the international community," Abe said.
The Prime Minister said Japan held a national security meeting on Thursday and continued to be "in close contact with the US, South Korea, and the international community to monitor the situation and to protect the safety and assets of the Japanese people."
If confirmed to be a missile test, it would be Pyongyang's 13th since May .
North Korean leader Kim Jong Un reportedly inspected the test-fire of a "super-large multiple launch rocket system" by the country's Academy of Defense Science and "expressed great satisfaction over the results," according to North Korean state news agency KCNA.
The operation was intended to test the "technical superiority of the weapon system and its firm reliability," KCNA said.
The uptick in weapons testing comes amid increasing friction between North Korea and its main adversaries, South Korea and the United States. Nuclear negotiations between Washington and Pyongyang have been at an impasse for weeks, and North Korea recently stated it is no longer interested in holding talks with the US .
Thursday's launch took place on Thanksgiving morning in the US, and the symbolism might be significant. North Korea has previously conducted missile tests on important American holidays. Its first successful test launch of an intercontinental ballistic missile (ICBM) came on July 4 -- US Independence Day -- in 2017 . North Korean state media went on to call that launch part of a "package of gifts" for "American bastards."
It also comes almost exactly two years after North Korea test-fired its Hwasong-15 ICBM, which analysts believe could target much of the United States with a nuclear warhead.
Those launches preceded the flurry of summit diplomacy between North Korean leader Kim Jong Un, South Korean President Moon Jae-in and US President Donald Trump.
But nuclear talks between Pyongyang and Washington have essentially been on ice since early October, when the two sides met in Stockholm. That ended abruptly and without any agreement, and North Korea would go on to conduct two missile tests later that month .
Washington and Seoul postponed military drills scheduled for mid-November in an attempt to convince North Korea to return to the negotiating table, but Pyongyang rebuffed those efforts and went ahead with its own drills.
US Defense Secretary Mark Esper called North Korea's response "disappointing," but said he did not "regret trying to take the high road, if you will, and keep the door open for peace and diplomacy if we can move the ball forward."
However, the clock could be ticking. North Korean leader Kim said in an important policy speech in April that he would give the Trump administration until the end of the year to change its negotiating strategy. It is unclear how serious that deadline is.