"North Korea fired an unidentified projectile eastward," the Joint Chiefs of Staff said in a statement, without giving further details.

Pyongyang carried out an unprecedented seven weapons tests in January, including of its most powerful missile since 2017, when leader Kim Jong Un baited then-US president Donald Trump with a spate of provocative launches.

But the North paused testing during the Beijing Winter Games, possibly out of deference to only major ally China, analysts have said.

North Korea also warned last month that it could abandon its self-imposed moratorium on testing nuclear and long-range weapons, which have been on hold since 2017.

The North's fresh sabre-rattling comes at a delicate time in the region, as South Korea gears up to elect its next president on March 9.

Experts say Pyongyang could use its next key anniversary -- the 110th birthday of Kim Il Sung on April 15 -- to carry out a major weapons test.