North Korean leader Kim Jong Un looks at a rocket warhead tip after a simulated test of atmospheric re-entry of a ballistic missile, at an unidentified location in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on March 15, 2016. REUTERS/KCNA

TOKYO (Reuters) - Japan is always gathering and analysing information on North Korea’s nuclear missile situation with great interest, its top government spokesman said on Tuesday.

Chief Cabinet Secretary Yoshihide Suga told a news conference that the government was taking all possible measures for warning and surveillance of North Korea.

North Korea declared on Sunday it could test-launch an intercontinental ballistic missile (ICBM) at any time from any location set by leader Kim Jong Un, saying a hostile U.S. policy was to blame for its arms development.