South Korean President Lee Jae Myung on Saturday ordered an investigation into the alleged drone incursion into North Korea, according to the Seoul-based Yonhap News Agency.
North Korea earlier on Saturday accused South Korea of two separate fresh drone incursions, one earlier in January and another in September.
South Korean Defense Minister Ahn Gyu-back denied the South Korean military's involvement in the drone incursions and said that they were not models operated by Seoul.
Lee warned that if the allegations are proven true, they would amount to "a serious crime that threatens peace on the Korean Peninsula and national security," urging the military and police to conduct a swift and thorough investigation.
He also acknowledged the possibility that the drones may have been operated by a private individual or group.
Accusations by Pyongyang came a few days after Lee had sought Chinese mediation with North Korea.
Lee has sought to restore ties with Pyongyang since June, but North Korea has not responded.
