Seoul, South Korea CNN  — 

North Korea launched two suspected “short-range missiles” on Thursday, adding yet another complication into Pyongyang’s stalled negotiations with the United States and peace talks with South Korea.

The missiles were launched at 4:29 p.m. local (3.29 a.m. ET) and 4:49 p.m. local, and flew eastward, reaching flight ranges of 420 kilometers (260 miles) and 270 kilometers respectively, according to a statement from South Korea’s Joint Chiefs of Staffs.

They were launched from Kusong in North Korea’s northwest, said South Korea’s Defense Ministry, which also told CNN that the missiles had an altitude of around 50 kilometers and landed in the East Sea, also known as the Sea of Japan.

According to North Korean state news agency KCNA, Kim Jong Un himself oversaw the launches, which were designed to test the military’s “rapid reaction” ability. The young leader reportedly expressed satisfaction with the drill and stressed “the need to further increase the capability” of North Korean armed forces on its forefront and western front.

The US Department of Defense confirmed the missile launches to CNN.

People watch a TV showing a file photo of North Korea's weapon systems during a news program at the Seoul Railway Station in Seoul, South Korea.

South Korea’s President Moon Jae-in said North Korea may have launched the projectiles out of dissatisfaction with the outcome of the latest North Korea-US denuclearization talks at the Summit in Hanoi that ended without agreement earlier this year.

Moon told South Korea’s public broadcaster, KBS, that the launch of what South Korea’s military suspects were short-range missiles might be an attempt by North Korea to “pressure” and “push forward the denuclearization dialogue in the direction they want” and to “urge for [renewed] talks soon.”

Kusong has been the site of Pyongyang’s missile tests in the past, including a May 2017 test of a KN-17 intermediate range missile which traveled almost 500 miles before splashing down in the Sea of Japan/East Sea, hitting the water about 60 miles from Vladivostok in eastern Russia, according to US officials.

“The US and South Korean intelligence authority is conducting analysis for additional information,” JCS said in a statement. “Our military has currently heightened its surveillance and alertness against possible additional launches, whilst maintaining combat readiness in close coordination with the US.”

Blue House spokesperson Ko Min-jung, from the official residence of the South Korean President, said it is “very worried” about the projectile launch, saying it “does not help in improving inter-Korean relations.”

South Korea said it "suspected" North Korea had launched "two short-range missiles."

Thursday’s firing comes less than a week after North Korea tested several new weapons systems, the first confirmed launches of their kind since 2017.

North Korean state media reported that the launches conducted on Saturday were part of a “strike drill” to “check the operating ability of large-caliber long-range multiple rocket launchers and tactical guided weapons.”

But some weapons experts who analyzed the images of Saturday’s launch released by North Korea say that Pyongyang may have test-fired a new, more advanced type of short-range ballistic missile – the type of weapon that in theory could carry a nuclear warhead.

Michael Elleman, a missile defense expert at the International Institute for Strategic Studies, wrote in a piece for North Korean specialty site 38 North that the weapon bore similarities to a Russian ballistic missile called Iskander.

Regardless of what was fired, analysts worry that an uptick in weapons testing from the North Koreans could impact nuclear negotiations with the United States and South Korea. Talks between the three countries have been on the rocks since a February meeting between US President Donald Trump and North Korean leader Kim Jong Un ended abruptly and without an agreement.

North Korea has been particularly vocal in its opposition to recent joint military drills between the US and South Korea. Seoul and Washington previously held large-scale military exercises in the spring, but this year chose to scale those back to “reduce tension” with North Korea.

South Korean President Moon Jae-in and Kim agreed at a summit with Kim last year to “make joint efforts to alleviate the acute military tension and practically eliminate the danger of war on the Korean Peninsula.”

Moon and Kim’s meeting was part of a flurry of diplomacy intended to reduce tensions on the Peninsula, as Washington and Pyongyang traded heated threats amid North Korea’s repeated missile and nuclear tests.

North Korea’s test pause is among the most important factors that has enabled negotiations between Seoul, Pyongyang and Washington. But a renewed round of missile launches could force the US to adjust course, as Trump has hinted that it could imperil the progress made between the two sides.

“I’m not in a rush, I don’t want to rush anybody, I just don’t want testing. As long as there’s no testing, we’re happy,” Trump said ahead of his February summit with Kim.

Trump’s top diplomat in charge of North Korea, Stephen Biegun, arrived in Seoul yesterday for meetings with his South Korean counterparts.

Correction: A previous version of this article stated that one projectile had been launched from Sino-ri, citing South Korea's Defense Ministry. After further analysis, the ministry tells CNN that both launched from Kusong. Both locations are in northwestern North Korea.

CNN’s Jake Kwon, Brad Lendon, Barbara Starr and Bianca Britton contributed to this report