SEOUL, South Korea -- North Korea on Saturday fired what appeared to be a ballistic missile from a submarine off its northeast coast, South Korean defense officials said, Pyongyang's latest effort to expand its military might in the face of pressure by its neighbors and Washington.

The South Korean officials, who spoke to The Associated Press on condition of anonymity because of office rules, could not immediately confirm where the projectile landed. The Saturday evening launch of what the officials said was presumably a submarine-launched ballistic missile took place near the North Korean coastal town of Sinpo, where analysts have previously detected efforts by the North to develop submarine-launched ballistic missile systems.

A successful test from a submarine would be a worrying development because mastering the ability to fire missiles from submerged vessels would make it harder for outsiders to detect what North Korea is doing before it launches, giving it the potential to surprise its enemies.

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South Korea's Joint Chiefs of Staff said in a statement that the projectile fired by the North on Saturday traveled about 19 miles. It said a typical submarine-launched ballistic missile can travel at least 186 miles.

The North last test-launched a submarine-launched ballistic missile on Dec. 25, but that test was seen as failure, the Joint Chiefs of Staff said.

The U.S. State Department would not comment on the reports of Saturday's launch, but noted, "Launches using ballistic missile technology are a clear violation of multiple U.N. Security Council resolutions."

"We call on North Korea to refrain from actions that further destabilize the region and focus instead on taking concrete steps toward fulfilling its commitments and international obligations," said State Department spokesman John Kirby.

North Korea has recently sent a barrage of missiles and artillery shells into the sea amid ongoing annual military drills between the United States and South Korea. Pyongyang says the drills are a preparation for an invasion of the North. The firings also come as the North expresses anger about toughened international sanctions over its recent nuclear test and long-range rocket launch.

North Korea's belligerence may also be linked to a major ruling party congress next month meant to further cement leader Kim Jong Un's grip on power. Promoting military accomplishments could be an attempt to overshadow a lack of economic achievements ahead of the Workers' Party congress, the first since 1980.

While South Korean experts say it's unlikely that North Korea currently possesses an operational submarine that can fire multiple missiles, they acknowledge that the North is making progress on such technology.