US intelligence: 'Highly probable' North Korea tested hydrogen bomb

The bomb had an explosive yield of 140 kilotons, intelligence indicates.

As U.S. intelligence continues to assess the underground nuclear test the official cautioned there is a chance that waht North Korea tested may have been a fission bomb bolstered to convert it into a thermonuclear bomb, though not necessarily a Hydrogen bomb.

Hydrogen bombs have exponentially more explosive power than atomic bombs, which North Korea has previously tested.

North Korea sparked international condemnation following its sixth underground nuclear test.

He added: "I can tell you that North Korea is behaving badly and it has to stop."

Following the blast, a U.S. intelligence official had described the U.S. as "highly confident" that North Korea had tested "an advanced nuclear device" that was not inconsistent with North Korea’s claims.

Afterward, some other officials advanced that further, saying intelligence assessments determined it was "possible" that North Korea had tested a hydrogen bomb.

On Thursday, an Air Force WC-135 “Constant Phoenix” monitoring aircraft flew from Kadena Air Force Base in Okinawa to detect any radioactive isotopes that may have made it into the atmosphere.