North Korea launched two unidentified projectiles on Thursday near Wonsan, an area along the coast, South Korean and Japanese officials said. The Pentagon did not immediately comment on the launch, but a senior U.S. official said the Trump administration was aware of the reports of a short-range projectile launched from North Korea. The official said the administration had no further comment..

South Korean officials said one of the two missiles flew 430 miles, longer than initially suspected. South Korea earlier said both missiles flew 270 miles before landing in the waters off the country's east coast on Thursday.

South Korea's military later said that it and the United States had determined the second missile flew longer. It said it still categorized both missiles as short-range. South Korean officials told both the Reuters and AFP news agencies that the second missile launched on Thursday, the one which flew further, appeared to be of a new design, but analysis was still being conducted to confirm that.

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Japan's Chief Cabinet Secretary Yoshihide Suga told reporters in Tokyo that missiles did not reach Japanese territory or its 200-mile exclusive economic zone.

"We don't find any evidence that the launches are threatening Japan's security at this point," Suga said.

It was the first time North Korea had fired projectiles since President Trump and South Korean President Moon Jae-in met Kim Jong Un at the Demilitarized Zone in June.

North Korea has been ramping up the pressure on the U.S. and South Korea over their expected summertime military drills that it views as an invasion rehearsal. Last week, the North said it may lift its 20-month suspension of nuclear and long-range missile tests in response to the drills. President Donald Trump has considered the weapons moratorium a major achievement in his North Korea policy.

Some experts say the launches are likely a negotiating tactic by North Korea, aimed at expressing its displeasure with the drills in order to get an upper hand ahead of the possible resumption of talks. North Korea wants to get widespread sanction relief to revive its dilapidated economy, but U.S. officials want the country to take significant disarmament steps before they give up the leverage provided by the sanctions.

It was the first such launch since Seoul said North Korea fired three short-range missiles off its east coast in early May. Many experts said at the time that those missiles bore a strong resemblance to the Russian-designed Iskander, a short-range, nuclear-capable ballistic missile that has been in the Russian arsenal for more than a decade.

CBS News correspondent Ramy Inocencio reports that analysts believe the missiles fired Thursday were variants of the rockets fired by the North in May. They were launched from mobile launchers, which makes them more difficult to detect. The analysts said the missiles are believed to be nuclear capable, and their small size and fast speed makes them difficult for missile defense systems to track and destroy.

President Trump dismissed the May launches as "very standard," and said they wouldn't change his relationship with Kim.

Inocencio notes that Kim was photographed earlier this week inspecting a new submarine, showing off the North's purported military developments. The chest-beating by the Kim regime could keep the diplomacy stalled, said Inocencio, and North Korea's Foreign Minister is reportedly no longer planning to attend a regional security summit next month, where he had been expected to meet Secretary of State Mike Pompeo.

During a third summit at the Korean border late last month, Trump and North Korean leader Kim Jong Un agreed to resume nuclear negotiations, which had been deadlocked since their second summit in Vietnam in February ended without an agreement because of disputes over U.S.-led sanctions. Both launches in May and on Thursday won't end that weapons test moratorium, which applies to firing intercontinental ballistic missiles.

North Korean state media said Tuesday that Kim inspected a newly built submarine and ordered officials to further bolster the country's military capabilities. The Korean Central News Agency said the submarine's operational deployment "is near at hand."

After analyzing North Korea-dispatched photos of the submarine, experts said the submarine likely has three launch tubes for missiles. South Korean government documents say North Korea has about 70 submarines, but analysts say they mostly have a single launch tube.

The construction of such a new submarine suggests North Korea has been increasing its military capability despite nuclear diplomacy that it began with the United States early last year.

The latest launches came amid a recent flare-up of tensions on the Korean Peninsula after South Korean fighter jets on Tuesday fired hundreds of warning shots to repel a Russian reconnaissance plane that Seoul says violated its territorial airspace.