North Korea fires two missiles as its rivals meet

North Korea test-fired two medium-range ballistic missiles Wednesday, South Korea and the United States said. Pyongyang’s defiant move came during a rare three-way summit of its rivals Seoul, Tokyo and Washington that focused on the security threat posed by the North.

The launch of the Rodong missiles – for the first time since 2009 – is a violation of U.N. Security Council resolutions and marks a big escalation from a series of shorter-range rocket launches the North has conducted in recent weeks to protest continuing annual military drills by Washington and Seoul that the North claims are preparation for an invasion.

The missiles flew about 403 miles off North Korea's east coast early Wednesday morning, South Korean Defense Ministry spokesman Kim Min-seok told reporters. It was not immediately clear where the missiles splashed down. Kim said the missiles were likely fired from a mobile launcher.

State Department deputy spokesperson Marie Harf said the U.S. is closely monitoring the development, “to take the appropriate measures” and “to address the threat to global security posed by the DPRK’s (North Korea’s) nuclear and ballistic missile programs.” North Korea did not issue any maritime notifications warning, she said.

“Coming on the heels of the DPRK’s March 3 and February 27 Scud launches," Harf said, Wednesday's missile launches "represent a troubling and provocative escalation that the United States takes very seriously.” She said that “launches using ballistic missile technology are a clear violation of U.N. Security Council resolutions.”

The launches come on the fourth anniversary of the sinking of a South Korean warship that Seoul and other nations blame on a North Korean torpedo. Pyongyang has denied involvement in that attack, which killed 46 sailors.

The missile launches also pose a big challenge to what had been recently improving relations between Pyongyang and Seoul.

A year after threatening each other with war, the bitter rivals had restored some trust and held reunions of families divided by the Korean War of the early 1950s. The Korean Peninsula remains officially at war because that conflict ended with an armistice, not a peace treaty.

North Korean state media made no immediate comment on the launches.

North Korea is thought to have a handful of rudimentary nuclear bombs, but most analysts do not believe Pyongyang has yet mastered the ability to build warheads small enough to mount on a missile that could threaten Tokyo and U.S. military bases in Japan. In attempt to achieve that goal, Pyongyang has conducted several long-range rocket tests in recent years and, a year ago, its third nuclear test. Talks aimed at ending the North's nuclear program, meanwhile, have been stalled since 2009.

The most recent launches came as U.S. President Barack Obama, Japanese Prime Minister Shinzo Abe and South Korean President Park Geun-hye met Tuesday in the Netherlands to discuss North Korea's security threat. It was Park and Abe's first face-to-face meeting since they both took office more than a year ago. Many in Asia are angry over Japan's treatment of historical issues related to World War II and Tokyo's colonization of the Korean Peninsula in the first half of the 20th century.

A North Korean diplomat on Monday criticized the U.S. for conducting military exercises near its borders, and accused Washington of undermining the prospect of improved relations with South Korea.

Analysts say the impoverished North chafes against the drills, which Washington and Seoul call routine and defensive in nature, because it has to spend precious resources responding with its own exercises. Last year, North Korea responded to international condemnation of its third nuclear test and the annual springtime U.S.-South Korean military drills by threatening nuclear strikes on Washington and Seoul.

The North's response to the military exercises this year had been more muted because of what analysts see as a desire by Pyongyang to use improving ties with Seoul to win badly-needed aid and outside investment.

Al Jazeera and The Associated Press