SEOUL, South Korea -- The U.S. and South Korean military said North Korea has fired several unidentified projectiles into the sea in what appears to be the latest weapons tests for the country that has been rapidly expanding its nuclear weapons and missile program.

Initial assessment indicates three short-range ballistic missile launches, the U.S. Pacific Command said in a statement. Although the U.S. Pacific Command initially said the first and third missiles failed in flight, CDR Dave Benham, the director of media operations, said these two missiles flew approximately 250 miles, or 155 kilometers.

The second missile appears to have blown up almost immediately, the U.S. military said.

Get Breaking News Delivered to Your Inbox

It's not clear what North Korea was trying to do by launching these three missiles in the span of 30 minutes, CBS News' national security correspondent David Martin reports.

Seoul's Joint Chiefs of Staff (JCS) said Saturday that that the projectiles were fired from an area from the North's eastern coast and flew about 250 kilometers, or 155 miles.

The three launches occurred near Kittaeryong, North Korea, the U.S. Pacific Command said.

The JCS says the South Korea and U.S. militaries were analyzing the launch. South Korea's presidential office has convened a National Security Council meeting to discuss the issue, Yonhap reports.

The launch comes weeks after North Korea created a tense standoff with the United States by threatening to lob some of its missiles toward Guam.

North Korea also successfully flight-tested a pair of intercontinental ballistic missiles in July that analysts say could reach deep into the U.S. mainland when perfected.

North Korea's state media earlier on Saturday said that leader Kim Jong Un inspected a special operation forces training of the country's army that simulated attacks on South Korean islands along the countries' western sea border in what appeared to be in response to the ongoing U.S.-South Korea war games.

Kim reportedly told his troops that they "should think of mercilessly wiping out the enemy with arms only and occupying Seoul at one go and the southern half of Korea."

The Korean Central News Agency said that the "target striking contest" involved war planes, multiple-rocket launchers and self-propelled guns that attacked targets meant to represent South Korea's Baengnyeong and Yeonpyeong islands before special operation combatants "landed by surprise" on rubber boats.

The border islands have occasionally seen military skirmishes between the rivals, including a North Korean artillery barrage on Yeonpyeong in 2010 that left two South Korean marines and two civilians dead.

Earlier this week, both President Trump and Secretary of State Rex Tillerson remarked on North Korea's restraint since the U.N. slapped sanctions on the country for its missile tests.

White House press secretary Sarah Huckabee Sanders said Mr. Trump has been briefed and the White House is monitoring the situation.