North Korean Cold War-style spy transmissions spark nuclear terror attack fears

North Korea has started sending out Cold War-style coded radio messages for the first time in 16 years, prompting fears of an imminent attack on its southern neighbour or even America.

The secretive state appears to be once again using a "numbers station" to broadcast bizarre and spooky communications over the airwaves.

These radio stations were famously used by 20th century spies to send transmissions featuring voices reading out long strings of numbers which contain coded messages.

Last Friday at 12.45, a shortwave broadcast came from North Korea in which a female voice: “From now on, I will give review work for the subject of mathematics under the curriculum of a remote education university for exploration agents of the 27th bureau.”

"South Korean intelligence is reportedly scrambling to find out why Pyongyang resumed this type of communication 16 years after its last such message, particularly in the digital age when it could have simply given out orders via the internet," wrote the newspaper Korea Joongang Daily.

"The revelation has put the government on high alert over possible strikes against facilities in the South by agents sent by the North."

Pyongyang commonly used numbers stations until 2000, when it attended a summit with the South.

The transmissions began as North Korea test-launched three ballistic missiles, raising the ominous possibility that an attack is being planned.

Last month North Korea claimed to have successfully launched a missile with a range of 3,000 miles, which Kim Jong Un declared has the ability to reach America.

International condemnation was swift, with the United States and Japan labelling the launches a clear violation of UN resolutions, and South Korea vowing to push for tighter sanctions on Pyongyang.

The UN Security Council has banned North Korea from using of ballistic missile technology.

But it ignored this order to carry out a test launch just days after American intelligence reports and South Korean data revealed an increase in activity at a nuclear test site in Punggye-ri.