SEOUL, Korea, Republic Of -- The U.S. and South Korea have determined that two projectiles launched by North Korea were short-range missiles, a South Korean military official said Friday, a day after the North's second launch in five days raised jitters about an unraveling detente between the Koreas and the future of U.S.-North Korea nuclear negotiations.

The weapons flew 420 kilometres (260 miles) and 270 kilometres (167 miles), respectively, on Thursday with an apogee of 45 to 50 kilometres (28 to 31 miles), according to Seoul's Joint Chiefs of Staff and Defence Ministry. The launches were seen as a possible North Korean warning toward Washington over deadlocked nuclear negotiations as the two sides continue to struggle with mismatched demands on sanctions relief and disarmament.

North Korea's state-run Korean Central News Agency said Friday that leader Kim Jong Un helped guide the weapons tests on Thursday and learned about "various long-range strike means," but the statement from the propaganda services didn't specify the type of missiles fired. The North's official Rodong Sinmun newspaper published photos showing Kim, equipped with binoculars and smiling widely, observing the firing of rocket artillery and what appeared to be a short-range ballistic missile fired from a launch vehicle.

South Korea's National Intelligence Service told lawmakers in a closed-door briefing on Friday that the missile is possibly part of a new North Korean weapons system, lawmaker Kim Min-ki said.

Experts say the missile was identical to the one that North Korea launched on Saturday, which appeared to be a solid-fuel missile modeled after Russia's Iskander short-range ballistic missile system. The Rodong Sinmun photos showed the North used a tracked launch vehicle on Thursday, unlike Saturday when it used a wheeled vehicle.

Some analysts say the new missile is potentially capable of delivering warheads and striking targets within the entire Korean Peninsula. It's unclear how closely the missile matches the capabilities of the Iskander, which can be manoeuvred during flight to improve its chances of evading missile defence systems.

The South Korean military official said the South Korean and U.S. militaries are continuing to jointly analyze details from the launch. He didn't want to be named, citing office rules.

What was launched Thursday is a crucial detail, as North Korea is banned by the United Nations from testing ballistic missiles. A major missile test could result in more sanctions, and North Korea's so far unsuccessful push for large-scale sanctions relief is at the heart of the current diplomatic impasse with Washington.

South Korea's military said the two missiles were launched from the town of Kusong in North Pyongan province, where North Korea conducted its first successful flight tests of its Hwasong-12 intermediate-range missile and Hwasong-14 intercontinental ballistic missile, both in 2017.

Kusong also has missile test facilities that were critical to the development of North Korea's solid-fuel Pukguksong-2, which was successfully flight-tested for the first time in February 2017, in the North's first missile test after President Donald Trump took office.

The latest launches came as U.S. Special Representative for North Korea Stephen Biegun visited South Korea, and hours after the North described its tests on Saturday as a regular and defensive military exercise. North Korea also ridiculed South Korea for criticizing those launches.

Trump told reporters the weapons were smaller, short-range missiles, but said "Nobody's happy about it." He has met with Kim Jong Un at two summits but said Thursday at the White House that "I don't think they're ready to negotiate."

South Korean President Moon Jae-in urged North Korea to refrain from actions that could impede diplomacy. In an interview with the KBS television network, Moon also said Seoul will explore various options to help revive the talks, including providing food aid to the North and pushing for his fourth summit with Kim.

Moon's office earlier said the North Korean launches were "very concerning" and detrimental to efforts to improve inter-Korean ties and ease military tensions on the Korean Peninsula.

Japanese Defence Minister Takeshi Iwaya said Friday that Tokyo finds it "extremely regrettable" that North Kora fired short-range ballistic missiles in violation of UN Security Council resolutions. He said none of the missiles reached Japanese territory and there was no immediate impact on Japan's security.

Some analysts have said that if North Korea resumes testing the kind of longer-range banned ballistic weapons that it fired in unusually large numbers in 2017 -- when many feared a U.S.-North Korea standoff could end in war -- it may signal that North Korea is turning away from diplomacy.

The tensions in 2017 were followed by a surprising diplomatic outreach by North Korea in 2018, when Kim attended summits with the South Korean and Chinese presidents and with Trump. But North Korea has not received what it wants most from its summitry: relief from punitive sanctions imposed over its nuclear and missile programs.

In Geneva on Thursday, North Korean Ambassador Han Tae Song likened the economic sanctions to "crimes."

With the consecutive weapons launches, North Korea is pressuring South Korea to turn away from the United States and support North Korea's position more strongly, said Du Hyeogn Cha, a visiting scholar at Seoul's Asan Institute for Policy Studies. Following the collapse of the Trump-Kim meeting, North Korea demanded that South Korea proceed with joint economic projects that have been held back by U.S.-led sanctions against the North.

By firing weapons that directly threaten South Korea but not the U.S. mainland or its Pacific territories, North Korea also appears to be testing how far Washington will tolerate its bellicosity without actually causing the nuclear negotiations to collapse, Cha said.

"To the United States, the North is saying 'don't push me into a corner.' To South Korea, the North is saying the inter-Korean peace agreements could become nothing if Seoul fails to coax major concessions from the United States on behalf of the North," Cha said.

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Associated Press writer Mari Yamaguchi in Tokyo contributed to this report.