Turkish media reports say five senior police officials in Istanbul have been removed from duty, suggesting that Turkish Prime Minister Recep Tayyip Erdogan was fighting back against a probe targeting key allies.

Dozens of people, including the sons of at least two government ministers, have been detained for questioning in a police corruption and bribery operation launched Tuesday. Erdogan has suggested the probe is a politically motivated plot to harm his government.

The private Dogan news agency said five police chiefs who were removed from office Wednesday included commissioners in charge of combatting organized crime, smuggling, and criminal financial activity. Dogan says the officials oversaw the operation.

The state-run Anadolu Agency, meanwhile, raised the number of people detained as part of the investigation to more than 50.