Turkey's top judicial body on Tuesday expelled four prosecutors and a judge who oversaw a massive corruption investigation that tarnished the Islamic-rooted government and reached into the inner circle of President Recep Tayyip Erdogan.

The Supreme Board of Judges and Prosecutors (HSYK) voted to bar prosecutors Zekeriya Oz, Celal Kara, Muammer Akkas and Mehmet Yuzgec, as well as judge Suleyman Karacol, state-run Anatolia news agency reported.

They were expelled for "undermining the honor of their profession" and "damaging the influence and reputation of their public post," Anatolia said.

Oz immediately took to Twitter to denounce the ruling as "null and void."

"Shame on the HSYK for acting upon orders from above, violating the laws and the constitution and not even taking our statements," he wrote.

The prosecutors and judge, who have already been removed from their positions, had been accused of abusing their authority by leading the December 2013 graft probe that rocked then-prime minister Erdogan's government, claiming four of his ministers.

The corruption case was later dropped due to a "lack of evidence."

Erdogan, who came out fighting from the crisis and won the presidency in August, claimed the investigation was an attempted "judicial coup" staged by US-based Muslim cleric Fethullah Gulen and his followers in Turkish state administrations.

The president has promised no mercy in the fight against Gulen, and authorities have effectively purged the police force and judiciary of pro-Gulenist elements, arresting people considered close to the preacher.

In the tense run-up to June 7 parliamentary elections, Erdogan has signalled the crackdown against Gulen supporters will widen, vowing "arrests would definitely continue."