South Korea's defence ministry said Thursday that a joint analysis with US experts of three crashed drones recovered in recent months proved they had all been flown from North Korea.
Ministry spokesman Kim Min-Seok said a joint investigation team had confirmed the provenance of the unmanned aerial vehicles (UAVs) after analysing the GPS coordinates stored in their systems.
"We have confirmed that all three UAVs originated from North Korea," Kim said.
"This is a clear military provocation," he added.
The drones were recovered in three different locations near the inter Korean border between March 24 and April 6.
One crashed due to an engine problem, while the other two ran out of fuel.
Although extremely rudimentary in design, they were all equipped with cameras and had taken pictures of border areas and the capital Seoul, including the presidential palace.
North Korea has flatly denied any connection to the drones, and accused Seoul of "fabricating" a link in order to smear Pyongyang.
North Korea had displayed a set of what looked like very basic drones during a huge military parade held in Pyongyang last July to mark the 60th anniversary of the end of the Korean War.
And in March last year, state media reported leader Kim Jong-Un overseeing a military drill using "super-precision drone planes."
Still photographs of the exercise broadcast on state television showed what resembled air force target drones being flown into a mountainside and exploding.