North Korean state media said Monday that an investigation had "proved" South Korea's military sent a drone over Pyongyang to drop propaganda leaflets, calling it an infringement of sovereignty.
The nuclear-armed North has accused Seoul of sending unmanned drones into its airspace three times, which South Korea's military has denied.
North Korea's ministry of defence dismantled the control module from the remains of a crashed "enemy drone" and analysed the flight plan and log, state media reported.
The analysis "proved that the drone of the ROK military gangsters... intruded into the capital city of the DPRK", the official Korean Central News Agency reported, referring to both countries by the acronyms of their official names.
A graphic published by KCNA showed a flight route of the drone starting from South Korea's Baengnyeong island and landing in Pyongyang after crossing the western sea of the Korean peninsula.
Baengnyeong is the westernmost border island in South Korea and closer to Pyongyang than Seoul.
"The spokesman for the Ministry of National Defence stressed once again that the last warning to the dangerous and reckless, political and military provocation by the ROK military gangsters which went beyond the limit of patience has already been made," said KCNA.
It said if an incursion happens again, the South "will disappear forever by the merciless offensive of the DPRK".
Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, issued a separate statement saying Pyongyang would not send drones southwards.
But if such a situation did occur, Kim Yo Jong said, she would "like to see once how the dirty curs in Seoul bark. The world may also be curious about it".
South Korea's Defense Minister initially denied that South Korea had sent drones, but the Joint Chiefs of Staff later amended that position, saying in a statement they "cannot confirm whether the North Korean allegations are true or not".
