Seoul: Investigators said Friday they have requested an arrest warrant for a graduate student allegedly behind recent drone flights to North Korea. The 30-something student, surnamed Oh, is suspected of sending drones to North Korea four times to test their performance with the aim of making a profit from a drone business, according to the police.

According to Yonhap News Agency, the drones were set up to depart from Ganghwa Island in Incheon, west of Seoul, and fly over North Korea's Kaesong and Pyongsan before returning to Paju, northwest of Seoul. A military-police task force investigating the case sought the arrest warrant Thursday on charges of benefiting the enemy and violating aviation safety and military installation laws. The task force cited concerns the suspect may destroy evidence.

"(The flights) created tension between South and North Korea, putting the people of the Republic of Korea in danger," the task force stated. "We determined that it harmed our military interests, such as by exposing our military's affairs and leading to a change in our readiness posture." The task force has been investigating seven people, including Oh, in connection with the drone flights, including individuals allegedly involved in the aircraft's production and military and spy agency officials.

The joint investigation was launched last month after North Korea claimed South Korea infringed on its sovereignty with drone incursions in September and on Jan. 4.