CAIRO: Egypt's public prosecutor ordered 29 people to be detained for 15 days pending an investigation into accusations they spied for Turkey and joined a "terrorist" group, his office said Wednesday.

The 29 suspects - and others who are still at large - are accused of "spying in favour of Turkey and membership in an terrorist organisation", a statement said.

The suspects were accused of offering Egyptian citizens an international phone service, which was set up to spy on Egyptians and offer the information to Turkish intelligence.

They listened in on those calls to monitor the opinions of Egyptians on conditions in the country, and then leaked the information to Turkish intelligence services.

The suspects acted in agreement with "elements from the Turkish security and intelligence services and members of the international Muslim Brotherhood organisation" in a bid to help the Muslim Brotherhood take power in Egypt, the statement said.

The public prosecutor's office did not give a timeline for these alleged acts nor was it clear when the suspects were arrested.

The suspects were also accused of money laundering, illegal currency trade as well as setting up media entities abroad to disseminate fake news aimed at "stirring up public opinion against (Egypt's) state institutions", the statement said.

The statement said authorities searched the homes of the suspects and found computers equipped with surveillance programmes and other equipment to facilitate the international calls.

Relations between Egypt and Turkey have been strained since Egypt's army ousted president Mohamed Morsi in 2013.

Ankara denounced the move and called Morsi´s ouster a "coup".

Several members of Morsi's Moslem Brotherhood - now outlawed in Egypt - have sought refuge in Turkey, which also hosts pro-Brotherhood satellite television channels.