This file photo, released by North Korea's official Korean Central News Agency, shows the country's test-firing of a new 600 mm multiple rocket launcher, Sept. 13. Yonhap

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 (JCS) 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.

"The government sternly warns against North Korea's provocations," an official from the presidential office said in a press release. "The government is closely monitoring North Korea's provocative movements and preparing for a variety of possible provocations in order to protect the lives and safety of our people."

South Korea, the United States and Japan condemned the latest launches, as well as the North's disclosure of the uranium facility last week, during phone talks between their nuclear envoys, according to South Korea's foreign ministry.

The three sides called the launches "clear" violations of U.N. Security Council resolutions and agreed to maintain coordination to "sternly" respond to the North's threats, while monitoring the possibility of additional North Korean provocations, it said in a release.

The JCS also condemned the launches, saying they "seriously" threaten peace and stability on the Korean Peninsula.

The U.S. Indo-Pacific Command said it was consulting closely with South Korea and Japan over the launches, calling on the North to refrain from further "unlawful" and "destabilizing" acts.

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.

Including the latest launches, North Korea has fired ballistic missiles over 10 occasions this year. (Yonhap)