Seoul: North Korea has fired "a barrage" of unidentified short-range projectiles toward the ocean, according to the South Korean military.

South Korea's military has bolstered its surveillance in case there are additional weapons launches, and South Korean and US authorities were analysing the details of the Saturday launch.

People watch a TV showing a file footage of North Korea's missile launch in Seoul on Saturday. Credit:AP

The South initially reported that a single missile was fired, then said it was a barrage of missiles, but later issued a statement that said "several projectiles" had been launched and that they flew up to 200 kilometres before splashing into the sea toward the north-east. Experts say the North may increase these sorts of low-level provocations to apply pressure on the United States to agree to reduce crushing international sanctions

They flew for a range of about 70 to 100 kilometres from 9.06am (10.06 AEST), the JCS said, adding that South Korean and US authorities were analysing details of the missiles.