Two suspected North Korean missile launches drew Japanese condemnation on Friday, just days after the isolated country’s defiant leader Kim Jong Un threatened to carry out a series of nuclear warhead tests and missile launches.

Chief Cabinet Secretary Yoshihide Suga said North Korea shot off a medium-range ballistic missile at around 5:54 a.m. from the western part of Sukchon. It flew about 800 km and fell into the Sea of Japan about 650 km east of the Korean Peninsula. Suga said Tokyo lodged protest with North Korea through the embassy in Beijing, and that there is no report of damages caused to Japanese ships by the launch.

The U.S. officials said the second missile, fired about 20 minutes later, disappeared from radar in the early stage of its flight. Yonhap News reported that it may have exploded before reaching its target area, citing South Korean defense officials.

Both U.S. and South Korean defense officials believe the missiles were probably Nodongs fired from mobile launch vehicles.

Tokyo has yet to confirm details on the second missile or what type may be involved, but Defense Minister Gen Nakatani did tell reporters he has not ruled out the possibility they were Nodong missiles, which have a maximum range of 1,300 km and are capable of striking Japan. Kyodo News reported that Nakatani issued an order to destroy the missiles should they threaten Japanese territory, citing government sources.

Prime Minister Shinzo Abe denounced the North’s lates tprovocation, calling it a clear violation of the U.S. Security Council resolutions.

“We demand that North Korea refrain (from any provocative actions), and we are bracing for any contingency,” Abe said during the Upper House budgetary committee session.

Tensions have been simmering since Pyongyang carried out its fourth nuclear test on Jan. 6, followed by the launch of a long-range rocket that was seen as cover for another long-range ballistic missile test.

Friday’s launch is widely believed to be a blatant protest against the biggest joint military drills held by the United States and South Korea. The drills, underway since March 7, are often criticized by Pyongyang as a provocative rehearsal for invasion.

On March 10, the North fired two short-range missiles into the Sea of Japan. It also launched a Nodong missile in March 2014, while the U.S. and South Korea were staging joint drills.

Pyongyang’s continuous provocations come amid mounting international pressure against it. Japan and South Korea have already adopted their own sanctions and the U.N. Security Council earlier this month unanimously adopted a resolution that imposes the most stringent sanctions ever on the North. U.S. President Barack Obama on Thursday also signed an executive order implementing tough sanctions based on the resolution, further isolating a country that is already known as the hermit kingdom.

The newly imposed sanctions are aimed at weakening Pyongyang’s ability to further develop nuclear weapons. Pyongyang is believed to already have a small stockpile of nuclear weapons, though its ability to accurately strike targets has been questioned. Among the North’s ambitions is to develop a usable inter-continental ballistic missile that can strike the North America. Yet experts say it will take years for North Korea to develop that capability.

To diffuse such skepticism, the North has been flaunting its technological development.

The state-run Korean Central News Agency earlier this month reported that the country has succeeded in miniaturizing nuclear warheads to fit in ballistic missiles.

The state media on Tuesday also reported that North Korea successfully conducted a simulation of the atmospheric re-entry of a warhead. The technology, if actually developed, would give the North the ability to not only launch a long-range missile, but also guide it through re-entry and to a target, including the United States.

South Korea’s defense ministry said that Pyongyang is yet to acquire such technology. Yet experts say that the North could soon be testing an ICBM, which could further destabilize the security landscape of the Korean Peninsula and escalate military tensions.

Information from AFP-Jiji added