Turkish prosecutors on Friday dropped a case against 60 people, including the son of a former minister, in a corruption probe that has rocked the Islamic-rooted government, local media said.

An Istanbul prosecutor handling the probe into graft in Turkey's housing agency TOKI decided not to take the suspects to court, citing "lack of evidence" for his decision.

The suspects who escaped prosecution include Oguz Bayraktar, the son of former environment minister Erdogan Bayraktar, and construction tycoon Ali Agaoglu, the Dogan news agency reported.

They were detained in police raids in mid-December when the corruption scandal first erupted and charged with accepting and facilitating bribes for construction projects and securing construction permits for protected areas.

Some 30 other key allies of the prime minister, including the sons of two other cabinet ministers, are still facing charges for corruption, fraud and money laundering as part of the primary investigation. The three ministers have since resigned.

Erdogan has accused supporters of a former ally turned arch-rival, US-based Muslim cleric Fethullah Gulen, of instigating the graft probe to topple his government.

He has retaliated by sacking hundreds of police and prosecutors believed to be linked to Gulen and introducing curbs on the judiciary and the Internet.

In the latest development, Turkey's Supreme Board of Judges and Prosecutors (HSYK) approved a probe into three prosecutors and a judge who initiated the graft probe.

Prosecutors Zekeriya Oz, Celal Kara, Muammer Akkas had already been removed from their posts in the wake of the scandal, while the judge Suleyman Karacol, who approved the temporary freezing of the suspects' assets, had been stripped of his duties.

Erdogan's ruling Justice and Development Party has managed to emerge relatively unscathed from the scandal, scoring a resounding victory in March 30 local elections, winning 45 percent of the vote.