The presidential office says it believes North Korea sent the unmanned drones that recently crashed on a South Korean island in the Yellow Sea and in a city near the land border with the North.
 
Presidential office spokesman Min Kyung-wook told reporters on Wednesday that the top office received interim results through the national security office about the drones, noting the final results have not come out yet.
 
Min said the government plans to come up with countermeasures even if the drones are not from North Korea.
 
He said once military and intelligence authorities finish their investigation, the Defense Ministry, the Joint Chiefs of Staff and the Capital Defense Command will hold a meeting chaired by the national security office to devise the countermeasures and unveil them to the public.
 
On Monday, an unmanned drone crashed on Baengnyeong Island near the Yellow Sea border with North Korea, the same day the North fired artillery rounds into South Korean waters across the border.
 
Another drone was found a week before in Paju, a city near the Demilitarized Zone.