Both North and South Korea tested ballistic missiles on Wednesday, ratcheting up tensions exponentially in what was already one of the most volatile regions on the planet.

Pyongyang fired the first missiles on Wednesday, sending two into waters off the east coast of the Korean Peninsula five minutes apart, at 11:38 p.m. and 11:43 p.m. ET, according to Japan's Coast Guard.

Seoul followed that test less than three hours later, firing a new submarine-launched ballistic missile (SLBM) from the submerged 3,700-ton submarine ROKS Dosan Ahn Changho, South Korea's Defense Ministry said. The missile hit its target accurately, the ministry said without giving more details.

South Korean President Moon Jae-in was present for the test, the ministry said.

With the launch, South Korea becomes the seventh military in the world to successfully test and SLBM, the ministry said.

The other SLBM nations are also nuclear powers but South Korea does not have nuclear weapons.

Earlier, North Korea fired two unidentified ballistic missiles into waters off the east coast of the Korean Peninsula on Wednesday, according to South Korea's Joint Chiefs of Staff.

South Korea said the missiles covered a distance of about 500 miles while going as high as 37 miles.

Japan's Defense Ministry said the North Korean projectiles are believed to have fallen into waters outside its exclusive economic zone.

Still, Japanese Prime Minister Yoshihide Suga called the North Korean launches "outrageous," adding they "threaten the peace and security of our country and region."

While the U.S. military's Indo-Pacific Command in Hawaii said the North Korean test did not pose any "immediate threat" to the U.S. or its allies, it said in a statement that the launch "highlights the destabilizing impact of the DPRK's [Democratic People's Republic of Korea] illicit weapons program."

Wednesday's ballistic missile tests are Pyongyang's first since U.S. President Joe Biden took office in January and come just days after Pyongyang said it tested long-range cruises missiles on Saturday and Sunday.

North Korea is barred from testing ballistic missiles and nuclear weapons under international law. Previous such tests have been met with international opprobrium and sanctions from the United Nations Security Council.

Cruise missiles are propelled by jet engines. Much like an airplane, they stay closer to the ground, making them harder to detect. Most cruise missiles are not designed to carry nuclear warheads.

Ballistic missiles by comparison are powered only for a short portion of their flight. They are fired on an arcing path that for longer range versions takes them outside of Earth's atmosphere, and they can handle heavier payloads such as nuclear warheads.

The North Korean military unveiled two new missiles at parades last October and in January. One, which analysts said might be one of the largest in the world, was so big it needed to be put on an 11-axle truck.

But at the North's most recent military parade last week, there were no missiles to be seen, the parade ranks filled instead by armaments of the smaller battlefield variety.

On the South Korean side, the SLBM launch was one of a series of military tests performed by the country's military on Wednesday.

It also fired a long-range air-to-surface missile, releasing it from an aircraft, deploying its wings and flying it successfully on target, the ministry said.

That weapon, still in development, is designed to be used by South Korea's FK-21 fighters, stealthy jets that are in the prototype stage.

A statement from South Korea's Agency for Defense Development also said the country had succeeded in developing a new ballistic missile capable of carrying a heavier and stronger warhead. The missile is designed to take out concrete structures and tunnels, the agency said.

"This high-strength ballistic missile will augment our military's peacetime deterrence and in crisis will be used as core arsenal in projecting overwhelming response," the Defense Ministry said.

The ministry said a hypersonic cruise missile designed to strike enemy ships was developed as well. The statement called the new hypersonic much faster than missiles now in South Korea's inventory and said it will soon be deployed with South Korean military units.