A source from Turkish Prime Minister Recep Erdogan's office said they found suspected spy devices in the leader's bureau and house.
The Turkish source refused to point the finger directly at Gulen's organization, while other Turkish sources quoted in the article blamed figures in the state's attorney general's office and in the judicial branch of government.
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The official close to Erdogan said a report is scheduled to be published on eavesdropping in the coming days.
The source said that Erdogan is taking the issue seriously, and he sees the incident as a breach of natural security since eavesdropping on the prime minister is considered treason of the highest degree. He doesn't want a state within a state, the official said.
Erdogan, who was Gulen's partner and was helped by him to rise to power, sees the preacher and his movement as the cause behind the investigation into the prime minister's corruption affair. The former ally has a network of followers in the police and judiciary.
Since leak of the affair, Erdogan has purged hundreds of police officers and sought tighter control over the courts, raising alarm in Western capitals and shaking investor confidence in what was long one of the world's fastest growing economies.
In an apparent bid to force the opposition's hand, Erdogan said he could drop a controversial bill to give government greater sway over the naming of judges and prosecutors if the opposition agreed instead to changes to the constitution on control of the judiciary.
Reuters contributed to this report