The drones were recovered in three different locations in the South between March 24 and April 6.

The South's defence ministry last week called them "a clear military provocation" and said it had "smoking gun" proof that they had all been flown from North Korea.

On Sunday the North, repeating previous denials, said it has nothing to do with the drones "no matter how frequently the South Korean authorities cook up stories".

"The Park Geun-Hye group foolishly seeks to find a way out of the worst ruling crisis," an inspection group from the North's powerful National Defence Commission (NDC) said in a statement referring to the South's President.

The April 16 ferry sinking which killed more than 300 people is one of South Korea's worst peacetime disasters, made all the more shocking by the loss of many young lives.

Victims' families have been extremely critical of the government over the disaster, as more evidence emerges of lax safety standards and possible corruption among state regulators.

"It is the inveterate bad habit of the South Korean authorities to seek a way out by fabricating shocking cases and linking them with the North whenever they are driven into a crisis," the NDC group said.

The South's defence ministry said last week a joint investigation with US experts showed the drones had been flown from different locations and pre-programmed to fly over South Korean military installations before returning to the North.

North Korea displayed a set of what looked like very basic drones during a huge military parade in Pyongyang last July.

And in March last year, state media reported leader Kim Jong-Un overseeing a military drill using "super-precision drone planes".