Turkish security forces announced Friday that they have detained four suspects, including the nephew of the Gülenist Terror Group’s ringleader (FETÖ), in a counterterrorism operation in Istanbul.

The Istanbul police and the National Intelligence Organization (MIT) working in coordination captured Selman Gülen, FETÖ ringleader Fetullah Gülen’s wanted nephew, as well as his wife Nur Gülen and her parents, Bekir and Mine Öztürk.

The quartet had been hiding at the raided apartment for nearly a year, authorities said. Upon orders from FETÖ’s leader, they made deposits at Bank Asya, a now-defunct lender that was the heart of FETÖ’s financial arm.

The foursome also served in administrative positions at FETÖ foundations and charities; they were in constant touch with the organization’s senior members.

Evidence surfaced showing that Selman Gülen was still involved within FETÖ’s financial branch, authorities informed.

Security forces seized digital materials, as well as some $14,000 (TL 365,890), 560 Estonian kroons ($40) and two passports belonging to two different people.

The suspects were sent to the police department for questioning.

The operation came just days before the seventh anniversary of a coup d'etat FETÖ attempted on July 15, 2016.

FETÖ posed as a religious group for years under the leadership of Fetullah Gülen before it disclosed its true intention of toppling the government and creating chaos in the country in 2013 with two plots targeting people close to the government. Türkiye managed to stave off these attempts and launched operations against the group, which was designated as a national security threat.

In 2016, the terrorist group tried to seize power again, this time by staging a coup attempt with the aid of its infiltrators in the Turkish army. This attempt was quelled too, and the group faced heightened scrutiny.

Police have launched countless operations against the group since the 2016 coup attempt and hundreds of military infiltrators were discovered and arrested in investigations, while tens of thousands were arrested for links to the group.

The state of emergency declared after the coup attempt sped up the crackdown on the terrorist group's infiltrators. Some FETÖ members managed to flee abroad, while others are believed to still be hiding their ties to the group.

Several former members confessed to authorities that senior figures of the group trained them on how to avoid being detected while serving in the army, law enforcement or judiciary.