SEOUL, Aug. 6 (Xinhua) -- The Democratic People's Republic of Korea (DPRK) fired two short-range projectiles into its eastern waters early Tuesday, the fourth such launch in less than two weeks, South Korea's Joint Chiefs of Staff (JCS) said.

The projectiles, presumed to have been short-range ballistic missiles, were launched at 5:24 a.m. and 5:36 a.m. local time each near the DPRK's southwestern county of Kwail in South Hwanghae province, the JCS said in a statement.

Both traveled eastward about 450 km at an altitude of some 37 km. The projectiles flew across the Korean Peninsula, before splashing into the eastern waters. Their maximum speed was more than Mach 6.9.

The intelligence authorities of South Korea and the United States saw the projectiles bear the similar flight features to the short-range ballistic missiles the DPRK fired off on July 25, according to the JCS.

The exact type of the projectiles was under analysis, the JCS added.

The JCS said the South Korean military was maintaining defense posture and closely monitoring relevant situations in preparation for an additional launch.

Chung Eui-yong, top national security adviser for South Korean President Moon Jae-in, convened an emergency meeting with the intelligence agency chief and the defense minister, according to the presidential Blue House.

The DPRK's projectile firings came a day after South Korea and the United States began their joint annual military drills despite Pyongyang's strong opposition to it.

The South Korea-U.S. computer-simulated command post exercise (CPX) was forecast to last for about three weeks.

Following the test-launch of short-range projectiles on July 25, the DPRK sent warnings against the planned South Korea-U.S. military exercises and Seoul's adoption of the U.S.-made stealth fighter jets.

Since then, Pyongyang fired off six more short-range projectiles, including the two launched earlier in the day.