National Security Adviser Kim Sung-han was briefed on North Korea's firing of a rocket launcher and monitored South Korea's military's readiness, the presidential office said Sunday night. 

“From 7 p.m. to 8:08 p.m, Kim received a report from the Joint Chiefs of Staff at the National Crisis Management Center regarding North Korea's estimated launch of a rocket launcher into the Yellow Sea and checked the South Korean military's readiness,” the office said in a press statement. 

The Joint Chiefs of Staff said earlier in a text message to reporters that it had detected “trajectories” believed to be artillery fire from around 6:21 p.m. to 6:37 p.m. It gave no additional details, such as the exact number of shots or where they were fired from.

The presidential office said, "The National Security Office is closely monitoring the situation in preparation for the possibility of additional launches by North Korea."

The government did not plan to publicize the rocket fire, but it did because of a media inquiry. 

“As has been announced in the past, conventional rocket launches like today are not announced at the government level,” the office said. But it added that the NSC informed the press of the results of the meeting due to media inquiries after the situation occurred and the Joint Chiefs of Staff confirmed the related facts. 

It is the first time that North Korea has fired a rocket launcher since June 12. 

The South Korean government detected several suspected North Korean rockets but announced them to the media 12 hours later. At the time, President Yoon Suk-yeol told reporters, "If the rocket is equivalent to a missile, we will take (more severe) measures accordingly. But yesterday's rocket is not seen as equivalent to a missile, so we took necessary measures."