North Korea said early Sunday that it had developed a hydrogen bomb that could be loaded into the country's new intercontinental ballistic missile.
The claim from Pyongyang came via official state media. The Korean Central News Agency said leader Kim Jong Un had inspected the device at the country's Nuclear Weapons Institute.
KCNA quoted Kim as describing the weapon as a "thermonuclear weapon with super explosive power, made by our own efforts and technology." He also was quoted as saying that all components of the hydrogen bomb were "100 percent domestically made."
The report included a picture of Kim dressed in a black uniform, posing with a metal object.
U.S. President Donald Trump and Japanese Prime Minister Shinzo Abe, speaking by phone Saturday, stressed the need for close cooperation between their two countries and South Korea in the face of the growing nuclear threat from North Korea, according to a White House statement.
The two leaders also agreed that pressure must be raised on North Korea, Abe told reporters.
On Friday, the leaders of the United States and South Korea spoke by telephone about North Korea, reaffirming the need to bring Pyongyang back to the negotiating table by applying maximum sanctions and pressure, according to the office of South Korean President Moon Jae-in.