North Korea has fired an intercontinental ballistic missile, according to South Korea’s joint chiefs of staff and American military officials.

The missile flew eastward and the South Korean military was analysing details with the US, Yonhap news agency said. The Pentagon said it believed the projectile was an intercontinental ballistic missile that travelled roughly 1,000 km before plunging into the Sea of Japan. Japanese broadcaster NHK reported that the missile remained airborne for 50 minutes and likely landed in the waters of the country’s exclusive economic zone, citing the country’s defense ministry.

Donald Trump was briefed while the missile was “still in the air”, White House Press Secretary Sarah Huckabee Sanders said, and Japanese Prime Minister Shinzo Abe convened a meeting of cabinet officials. The South Korean military said it quickly responded with a missile test of its own.

Japanese officials had been bracing for an imminent missile launch, saying they had detected suspicious radio signals. North Korea has menaced Japan in recent months, firing a ballistic missile over Hokkaido in September, which is the second time it hurled a missile over Japan and warning that the nation should be “sunken into the sea” by a nuclear strike.

The apparent launch marks the latest escalation of a global standoff with an increasingly assertive North Korea. The nuclear-armed hermit state has repeatedly displayed its military prowess in recent months, combining ballistic missile launches with threats of destroying Japan, the United States and the US territory of Guam. It tested a powerful hydrogen bomb for the first time.

Diplomatic constraints have failed to halt North Korea’s belligerence, with the country forging ahead with military tests despite successive rounds of United Nations sanctions targeting the country’s economy.