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 Tayyip 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.

Among dozens of officials dismissed in the latest sackings, Turkish media reported on Saturday that the deputy head of the banking watchdog BDDK and two department heads had been removed.

Five department chiefs were fired at the Telecommunications Directorate (TIB), a body that carries out electronic surveillance as well as serving as telecoms regulator, and a dozen people were fired at Turkey’s state channel TRT, including department heads and senior news editors.

Erdogan has suggested the graft inquiry, which has led to the resignation of three cabinet ministers and detention of businessmen close to the government, is an attempt by Fethullan Gulen, a U.S.-based cleric with influence among the police and judiciary, to undermine his rule.

Many of the people who have been fired are believed to be associated with the cleric’s Hizmet movement, which claims more than a million followers and runs schools and charities throughout Turkey.

Earlier in the week the government reassigned twenty high-profile prosecutors, stepping up the purge of the judiciary.

The government has also prepared a draft bill to tighten its grip on High Board of Judges and Prosecutors (HSYK), a panel that controls the appointment of all judges and prosecutors.

There were heated discussions and even fights among members of parliament during talks over the draft bill last week.

Erdogan, who has presided over an extended economic boom that has transformed Turkey and lifted millions of people from poverty, remains the country’s most popular politician.

He and his moderate Islamist AK Party have long battled for influence against the secularist military establishment that dominated Turkey for a century. His conflict with the judiciary, police and Gulen followers add to his list of enemies.

It is still not clear what effect the crisis might have a local elections approaching in March. Last year saw mass street demonstrations among Turks who accuse the prime minister of authoritarianism, but those protests did little to undermine Erdogan’s support among his conservative base of followers.