North Korea fired multiple short-range ballistic missiles in a northeastern direction on Wednesday, South Korea's military said, further ratcheting up tensions already heightened by its rare disclosure of a uranium enrichment facility last week.

The Joint Chiefs of Staff said it detected the launches at about 6:50 a.m. from the North's Kaechon area in South Phyongan Province, north of Pyongyang, and the missiles flew about 400 kilometers.

It did not provide further details, such as the number of missiles fired or where they landed.

The presidential office convened a meeting presided over by Yin Sung-hwan, the second deputy national security adviser, to discuss the launches and assess the security situation.

"We strongly condemn North Korea's missile launches that are clear acts of provocation seriously threatening peace and stability on the Korean Peninsula," the JCS said in a text message sent to reporters.

On Friday, North Korea disclosed its uranium-based nuclear facility, a day after firing multiple short-range ballistic missiles toward the East Sea.

The latest bouts of its saber-rattling have added to cross-border tensions caused by the North's launches of trash-filled balloons to the South.

The series of Pyongyang's provocative acts came amid lingering concerns that the recalcitrant regime could engage in major provocations to bolster its leverage ahead of the Nov. 5 presidential election in the United States.

The latest launch is suspected to have involved missiles similar to the North's Hwasong-11 family of missiles, previously launched in July.

The North fired two ballistic missiles in a northeastern direction on July 1, including one that landed in the East Sea and another that flew 120 km before disappearing off the radar and possibly falling inland, according to the JCS.

The North's state media said the next day the country had test-fired the new Hwasong-11Da4.5 missile at its maximum and minimum ranges, noting they are capable of being tipped with a 4.5-ton "super-large" warhead.

It notified of another test-firing the same month at the missile's medium range, but it apparently did not take place. (Yonhap)