Story highlights South Korean Defense Ministry calls the move a military provocation

North Korea launched four Scud missiles into East Sea, the South says

Launch may be an effort to show off North Korean capabilities, observer says

South Korea and the United States are conducting joint military exercises

North Korea launched four Scud missiles into the sea off its eastern coast Thursday, the South Korean Defense Ministry said.

The missiles were fired in the direction of Russia and fell into the sea, according to the Pentagon, which described the launch as a very low-level matter.

The missiles were fired just days after the start of annual joint military exercises between South Korea and the United States that North Korea opposes. The joint military exercises routinely spark tension between North Korea, South Korea and the United States.

For example, last year's exercises triggered weeks of heightened tensions between the nations and North Korean threats of nuclear war.

The South Korean and U.S. militaries have not been specific about where they are conducting their drills.

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The South Korean Defense Ministry said that the North had fired the Scuds in a northeasterly direction and that they probably fell into North Korean waters of the East Sea, which is also known as the Sea of Japan.

It was the first time North Korea had fired Scud missiles, which have a range that covers the whole of the Korean Peninsula, since 2009, South Korea said.

"We consider it to be threatening and a military provocation," said South Korean Defense Ministry spokesman Kim Ming-seok, although he acknowledged the firings may have been a test launch or part of military drills.

Foreign policy experts say the North Korean missile firings may not herald a repeat of last year's saber rattling from Pyongyang, which included threats of preemptive nuclear strikes against the United States and South Korea and the declaration that the armistice that stopped the Korean War in 1953 is null and void.

North Korea tested a multistage rocket with possible intercontinental potential in December 2012, and carried out a third nuclear test in February 2013. It was then stung by fierce international criticism and sanctions.

It reacted angrily when 2013's joint military exercises between South Korea and the U.S. involved stealth bombers simulating bombing attacks.

The conditions of Thursday's missile launch are different.

"It may be little more than regular military testing," said Michael O'Hanlon, a defense and foreign policy expert at the Brookings Institution. "I'm not persuaded it's a big deal or even a medium big deal, though."

The launch may also be an attempt by North Korea to remind the world and its own people that it has muscle, too.

Most observers say North Korea is still years away from having the technology to deliver a nuclear warhead on a missile, but it does have plenty of conventional military firepower, including medium-range ballistic missiles that can carry high explosives for hundreds of miles.

"North Korea's missile launch is merely part of their ongoing efforts to demonstrate to the world, and more importantly to their own people, what they are capable of. It is more showmanship than meaningful geopolitics," David Rothkopf, editor of Foreign Policy magazine, said Thursday. "It is not a surprise, and we should expect more of the same so long as this regime is in place."

Earlier this week, South Korea said a North Korean patrol boat strayed over the maritime border between the two countries several times. It eventually returned to the North's side of the border after warnings from South Korea.

Such infringements happen periodically, according to the South Korean Defense Ministry.