ISTANBUL (Reuters) - Turkish authorities on Monday detained 51 soldiers and nine others over alleged links to the U.S.-based cleric who Ankara says orchestrated the failed coup in 2016 against President Tayyip Erdogan, Istanbul police said.

Those detained were among 89 suspects whose detention was ordered in an investigation launched by Istanbul prosecutors and spread over nine provinces, it said.

Authorities have carried out such sweeps against suspected supporters of the cleric Fethullah Gulen on a regular basis since the July 2016 coup attempt, in which 250 people were killed. Gulen denies involvement.

Separately, Ankara prosecutors issued detention warrants for 13 senior officers, all with the rank of major and of whom three are on active duty, the Hurriyet newspaper said.

Turkey has detained around 160,000 people and dismissed nearly the same number of civil servants since the putsch attempt, the U.N. human rights office said in March. Of that number, more than 50,000 have been formally charged and kept in jail during their trials.

Turkey’s Western allies have criticized the crackdown, which took place under a state of emergency declared shortly after the coup attempt that remained in effect until July 2018.

Erdogan’s critics accuse him of using the failed putsch as a pretext to quash dissent. Turkey says the measures are necessary to combat threats to national security.