South Korea’s National Intelligence Service (NIS) on Tuesday claimed that North Korea did not “clearly detect” the deployment of U.S. B1-B bombers over the weekend and took no action in response, the head of the National Assembly’s Intelligence Committee said.

The U.S. Department of Defense (DOD) announced on Saturday that multiple Air Force B1-B Lancer bombers and F-15C Eagle fighters had flown a mission over international waters off North Korea’s east coast.

“It appears North Korea didn’t expect it all because [the flight happened] around midnight and it didn’t take any measures as [the B1-B Lancer fliers] are not clearly detected