A graduate student accused of sending drones to North Korea appeared at a court Thursday to attend his arrest warrant hearing. The 30-something student, surnamed Oh, faces charges of benefiting the enemy and violating aviation safety and military installation laws by flying drones to North Korea four times from September to January. Pyongyang reacted angrily by accusing South Korea of infringing on its sovereignty. The Seoul Central District Court will question Oh about the charges before deciding whether to issue a warrant for his arrest. A military-police investigation task force requested the warrant after concluding that the suspect had flown the drones to test their performance for a drone business. The aircraft 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, it said. The task force has been investigating seven people in connection with the drone flights, including Oh, those allegedly involved in the aircraft's production, and military and spy agency officials.