Turkey has extended a purge of official bodies to the banking and telecoms regulators and state TV, firing dozens of executives in moves that appear to broaden Prime Minister Tayypi Erdogan’s backlash against a corruption investigation.

The authorities have already sacked thousands of police officers, dozens of prosecutors and some state television officials in response to the corruption investigation, which has become the biggest challenge to Erdogan’s 11-year rule.

Investigators are believed to have been looking into allegations of corruption at a State-run bank and bribery involving big real estate projects, although details of their charges have not been made public.

The combative Prime Minister says the investigations, which began a month ago with arrests of high profile figures including the sons of three of his cabinet ministers, are part of an attempted “judicial coup”.

His opponents say they fear a purge of official bodies will destroy the independence of the judiciary, police and media.

“It’s like reformatting a computer. They are changing the whole system and people in various positions to protect the government,” said Akin Unver, assistant professor of international relations in Istanbul-based Kadir Has University.