Turkish authorities detained 57 people on Friday in an operation targeting former employees of the Istanbul stock exchange.

The detained are accused of having ties to the group of US-based cleric Fethullah Gulen, who Ankara blames for last July's failed coup attempt.

Prosecutors issued 102 arrest warrants against people who were dismissed from the stock exchange following the coup attempt.

The "HaberTurk" news outlet reported the detained are accused of using the encrypted messaging service ByLock, which the government says was used by coup plotters.

It also said those who were detained had carried out transactions to increase deposits at Bank Asya on behalf of the Gulen movement. Bank Asya was once closely tied to the Gulen movement. 

Nearly 50,000 people have been arrested in a post-coup purge of the police, military and bureaucracy. Tens of thousands more have been dismissed from their jobs.

The government accuses Gulen supporters of forming a "parallel structure" within the state.

The scale of the post-coup purges has raised concern over democracy and rule of law in Turkey. 

More than 400 Turkish soldiers, diplomats, judges and other government officials facing purges have applied for asylum in Germany, including more that 200 diplomatic passport holders. 

cw/rc (AFP, Reuters)