The 54-year-old officer, who was not named but was serving in a unit in the Athens region, appeared before military judicial authorities who ordered his detention, said the ministry source, who spoke on condition of anonymity.

The man's lawyer, Vassilis Chirdaris, said the suspect would appear before a military judge on Tuesday.

The officer faces charges of "espionage and illegal collection of information", which carries a potential life jail sentence, and "transmitting secret information of a military nature", with a sentence of up to 20 years' jail possible, the lawyer said.

The officer was arrested on Thursday. A Greek general staff statement said there was "clear evidence of criminal acts falling under the military penal code, namely the collection and transmission of classified military information to third parties, with the risk of harming national interests."

A military source, speaking on condition of anonymity, said the officer was part of an air force brigade who had access to sensitive national security details, including on technology.

The source and Greek media said the officer provided the information to contacts in China.

Media reports said the officer told investigators he was recruited a few months ago by a Chinese national.

Skai television said a western intelligence service detected the officer's transmissions and informed Greek intelligence and the military.