More security and anti-terrorism measures are being implemented after South Korea warned the United States that the Islamic State may be a threat to U.S. air bases in Korea.

Voice of America reported that South Korea is taking increased security precautions against ISIS after the South Korean National Intelligence Service said ISIS released a list of possible targets, including the 77 Air Force installations belonging to the U.S. and NATO in 21 countries. Four of these Air Force installations are located in South Korea.

“In order to strengthen the defense of the bases of the USFK (U.S. Forces in Korea), we will provide support if they request through cooperation with the Combined Forces Command,” said Korean Joint Chiefs of Staff spokesman Jeon Ha-gyu.

The South Korean National police said they are increasing patrols and strengthening investigations to promote the safety of those living in South Korea, according to Voice of America.

This includes protecting one employee at a South Korean welfare organization who was one of those specifically targeted on the list of people ISIS plans to attack, CNN reported.

U.S. Forces Korea made a statement about this Monday, saying they take security and the threats to it very seriously.

“Through constant vigilance and regular exercises with our South Korean counterparts, we remain prepared to respond at any time to any emerging threats,” USFK said in a statement cited by CNN. “USFK remains committed to ensuring the highest degree of security on the Korean Peninsula.”