Turkish police have detained at least 49 people in Istanbul and Ankara as part of a high-level corruption probe.

The sons of Interior Minister Muammer Guler, Economy Minister Yafer Caglayan and Environment Minister Erdogan Bayraktar were among those picked up in raids carried out by the financial crimes unit of the Istanbul Police Department

The operation – which is linked to a major investigation into alleged bribery connected to public tenders – is being widely interpreted as a challenge to the authority of Turkey’s Prime Minister Recep Tayyip Erdogan.

Turkish commentators believe the police raids could have been driven by Fethullah Gulen, a powerful Islamic cleric based in the United States. Gulen’s network of followers is known to include influential people within Turkey’s police and secret services.

Erdogan has not made any public comment on the operation, but said: “Those who are supported by dark circles from inside and outside the country cannot change the direction of Turkey.”