Fethullah Gülen, the Turkish religious leader and founder of the Gülen movement, died on Sunday evening at the age of 83 in the US state of Pennsylvania.

Gülen and his movement were accused by the Turkish government of plotting a failed military coup in July 2016 that left hundreds of Turks dead.

The movement itself denied involvement in the attempt to overthrow the Turkish government, but its role in the coup attempt is accepted throughout Turkish society and even among opponents of the ruling Justice and Development Party (AKP).

Herkul, an official website that publishes announcements about Gulen's activities, reported that the religious leader died at a hospital where he was being treated for chronic illnesses.

A detailed report on his health and information about his funeral would be released later, it said.

Gülen's death symbolizes the end of an era in Turkish politics.

Born in 1941, Gülen established himself as an imam in Turkey in the 1970s and eventually founded a well-organized religious movement to spread his faith.

The movement spread worldwide through a network of Turkish schools in more than 100 countries.

The movement functioned as an organization around the figure Gülen and claimed to follow the teachings of the late Islamic cleric and Sufi Said Nursi.

Gülen transformed the group into a full-fledged political movement whose followers practiced a form of entrism in which they actively recruited individuals and inducted them into key state institutions such as the police, judiciary and military.

First Alliance

At the start of this endeavor, the Gülen movement's politics dovetailed with the mainstream religious conservative movement led by current Turkish President Recep Tayyip Erdogan.

Conservatives welcomed attempts to make the military and judiciary less hostile toward religious groups, as these institutions played a crucial role in suppressing Islam's role in politics in Turkey's modern history.

In this climate of repression, Gülen traveled to the United States in 1999 for health reasons and never returned to Turkey.

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From its base in the United States, Gülen's movement founded Schools, a media conglomerate with magazines, newspapers and television stations, as well as business unions.

Networks of dormitories and student dormitories operating under the Gülen banner were used as recruiting grounds for the movement.

Well-educated or bright potential members were selected and their identities were masked or downplayed in order to easily enter government service.

When Erdogan took office as prime minister in 2003, Gülen already had a large network of followers within the state previously dominated by Turkish nationalists, secularists and others.

Erdogan allied with Gülen over the years to strengthen his own influence over the police and judiciary and undermine the military's influence in politics.

The alliance succeeded in bringing about constitutional changes in 2010, and people close to Gülen dominated top positions in the judiciary.

This was followed by indictments of senior generals and other powerful state figures accused of plotting to overthrow Erdogan, further weakening the military's role in Turkish politics.

Break with Erdogan

Erdogan's first dispute with Gulen came during the Israeli attack on a Gaza flotilla in 2010, when nine Turkish citizens were killed by Israeli soldiers aboard the Mavi Marmara, a ship that was trying to break the siege on the people of Gaza.

Gülen criticized the flotilla as too risky and criticized the government for letting the boat sail.

Another sore point was the peace process between the Turkish government and the Kurdistan Workers' Party (PKK) in 2013, which Gülen rejected.

Tensions simmered during the 2013 Gezi Park protests as Gülen opted for a neutral position while anti-government protesters staged the worst civil unrest against AKP rule since it came to power in 2002.

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The final breakthrough came in a corruption investigation in December 2013 against three ministers in the Erodgan government.

Erdogan accused Gülen and his movement of trying to use his people in the judiciary and police to overthrow his government through fabricated accusations.

After winning local elections a few months after the investigation, Erdogan began his crackdown on the Gülen movement by dismissing people associated with the group from civil service and declaring them terrorists.

The government also cracked down on Gülen-affiliated companies, media outlets and schools.

This crackdown intensified after the 2016 coup attempt, after which large-scale purges through emergency powers led to the dismissal and arrest of tens of thousands of civil servants and other state workers.

Gülen's presence in the United States also caused tensions with Washington, which did not immediately condemn the coup attempt.

Ankara's official demand for the US to send the cleric back to Turkey has been repeatedly ignored by the Americans, with Washington insisting there was insufficient evidence to implicate Gülen in the plot.

For its part, the Gulen movement, which operates more than 100 charter schools in the United States, has formed lobbying groups to pressure Congress over alleged human rights abuses in Turkey.

However, the group itself is characterized by divisions. Gülen's nephew, Ebuseleme Gülen, earlier this year accused the movement's leadership of knowing and condoning the 2016 coup attempt by empowering people close to Gülen to take part in the uprising and misleading Gülen about their involvement.

Turkish sources familiar with the matter told the media on Monday that there would be a leadership crisis within the movement following Gülen's death.

The sources said Cevdet Turkyolu, one of Gulen's deputies in Pennsylvania, and Abdullah Aymaz, the group's current leader in Europe, are expected to compete for the top job in the coming days.