SEOUL - The Democratic People's Republic of Korea (DPRK) test-fired three short-range projectiles into its eastern waters amid the ongoing the Republic of Korea-US war game, Seoul's military said Saturday.

The DPRK launched several unidentified short-range projectiles into the East Sea off the country's northeast region from an area near Gitdaeryong in Gangwon province at about 6:49 am local time (2149 GMT Friday), according to ROK's Joint Chiefs of Staff (JCS). The Gangwon province borders ROK's northeastern region.

The JCS said the projectiles flew about 250 km, but what the projectiles are was not known immediately.

It said the military authorities of the ROK and the United States were jointly analyzing the test-launches.

According to Yonhap news agency report citing an unknown source, a total of three projectiles were test-launched.

The first and third ones traveled around 250 km, and the second one exploded in the air immediately after taking off.

The test-firings came as the combined forces of the ROK and the United States kicked off their joint annual war game, codenamed Ulchi Freedom Guardian (UFG), on Monday. The war game would last until next Thursday.

The computerized command post military exercise has been denounced by the DPRK as a rehearsal for northward invasion. The scale of this year's war game was smaller than last year's.

The war game was the first large-scale the ROK-US military drill after the DPRK's tests in July of what it called an intercontinental ballistic missile (ICBM), called Hwasong-14.

Tensions de-escalated on the Korean Peninsula as Pyongyang and Washington stopped trading belligerent rhetoric.

US President Donald Trump warned Pyongyang of "fire and fury," and the DPRK warned Washington that it could fire intermediate-range ballistic missiles targeting the waters off the US island of Guam in the Pacific.

The DPRK delayed its missile strike plan to see what the US would do next, and Trump praised it as a "wise and well-reasoned" decision.

The DPRK test-firings were immediately reported to the ROK President Moon Jae-in who ordered the convening of the National Security Council (NSC) meeting of the presidential Blue House.

Chung Eui-yong, top national security advisor to President Moon, chaired the meeting for about an hour earlier in the day.

Senior presidential press secretary Yoon Young-chan told a press briefing that the DPRK projectiles were estimated to have been improved 300-mm multiple rocket launchers, saying the exact details were under study by the military.