North Korea fired a ballistic missile over Japan’s northern Hokkaido island into the sea early on Tuesday, prompting warnings to residents to take cover and drawing a sharp reaction from Japanese Prime Minister Shinzo Abe, Reuters agency reported.

The test, one of the most provocative ever from the reclusive state, came as U.S. and South Korean forces conduct annual military exercises on the peninsula, angering North Korea which sees them as a preparation for invasion.

North Korea has conducted dozens of ballistic missile tests under young leader Kim Jong Un, the most recent on Saturday, in defiance of U.N. sanctions, but firing projectiles over mainland Japan is rare.

“North Korea’s reckless action is an unprecedented, serious and a grave threat to our nation,” Japanese Prime Minister Shinzo Abe told reporters.

Abe said he spoke to U.S. President Donald Trump on Tuesday and they agreed to increase pressure on North Korea. Trump also said the United States was “100 percent with Japan”, Abe told reporters.

The U.S. disarmament ambassador said Washington still needed to do “further analysis” of the launch, but it will be the subject of a U.N. Security Council meeting later in the day.

“It’s another provocation by North Korea, they just seem to continue to happen,” U.S. envoy Robert Wood told reporters in Geneva.

“This is a big concern of course to my government and to a number of other governments,” Wood said before a session of the U.N.-sponsored Conference on Disarmament where North Korean Ambassador Han Tae Song was to speak.

South Korea’s military said the missile was launched from near the North Korean capital, Pyongyang, just before 6 a.m. (2100 GMT Monday) and flew 2,700 km (1,680 miles), reaching an altitude of about 550 km (340 miles).

Four South Korean fighter jets bombed a military firing range on Tuesday after President Moon Jae-in asked the military to demonstrate capabilities to counter North Korea.

South Korea and the United States had discussed deploying additional “strategic assets” on the Korean peninsula, the presidential Blue House said in a statement, without giving more details.

North Korea remained defiant.

“The U.S. should know that it can neither browbeat the DPRK with any economic sanctions and military threats and blackmail nor make the DPRK flinch from the road chosen by itself,” North Korea’s official Rodong Sinmun said, using the initials of the North’s official name, the Democratic People’s Republic of Korea.