Muslim cleric Fethullah Gulen, who was accused by Turkey of organising a failed 2016 coup, has died in exile in the United States aged 83, his movement said Monday.
Gulen, who had lived in the United States since 1999, was once a close ally of President Recep Tayyip Erdogan before the two became bitter enemies.
"The leader of this dark organisation has died," Foreign Minister Hakan Fidan said, vowing Turkey would continue to fight Gulen's "terrorist organisation" and its "treasonous" followers.
The charismatic preacher, who was stripped of his Turkish nationality in 2017, died in hospital on Sunday night, his nephew and a website close to him said.
Gulen moved to Pennsylvania in 1999, ostensibly for health reasons, and from there ran his Hizmet movement, which once operated 4,000 schools in Turkey and 500 others around the world.
Initially close to Erdogan, the pair fell out in 2013 and three years later the Turkish strongman accused him of masterminding the coup, dubbing Hizmet "the Fethullah Terror Organisation" (FETO).
Some 250 people died on July 15, 2016 when a rogue military faction tried to overthrow Turkey's government. Erdogan blamed Gulen supporters within the military.
Even beyond government circles, Gulen was widely disliked for his alleged role in the coup and the widespread influence once wielded by his movement behind the scenes.
"We had wanted him to be held accountable in Turkey," said main opposition leader Ozgur Ozel, describing Hizmet as "a terrorist organisation that infiltrated every corner of the state".
"Only its founder has died.. we need to be on guard against this insidious organisation."
Widely disliked within Turkey
Having helped Erdogan when he became prime minister in the early 2000s, Gulen's ties with him became strained in 2010.
Three years later, their relationship became pure enmity after a corruption scandal engulfed the Turkish premier's inner circle for which Erdogan blamed Gulen.
After the 2016 coup, authorities prosecuted more than 700,000 people and jailed some 3,000 Gulen followers for life over their alleged involvement in the putsch.
Bayram Balci, a researcher at the Paris Institute of Political Studies (Sciences-Po) told AFP the preacher's death would have little impact in Turkey.
"Since the break with Erdogan in 2010 and especially after the attempted coup in 2016, Gulen's image has been very bad.
"Few people held him in high esteem," he told AFP, saying many harboured a deep distrust of Gulenists from the time when they worked closely with Erdogan "in support of his repression".
In Germany, home to Europe's largest Turkish diaspora of three million people, a Hizmet spokesman said Gulen's death would not affect its work with up to 100,000 members and its management of some 250 associations.
No repatriation for burial
Although Gulen had wanted to be buried in the western Turkish city of Izmir, there was no chance Ankara would let his body be repatriated, meaning he would likely be interred in Pennsylvania, he said.
Turkey still regularly rounds up Gulen followers and demands their extradition from countries where Hizmet is active.
Despite Gulen's death, Turkey would continue to "fight against this organisation, which poses a national security problem", Justice Minister Yilmaz Tunc wrote on X.
But Balci said Hizmet "no longer represents any threat" as it was "no longer the big movement it once was" with its network of schools now reduced to just a handful operating mainly in Germany, the United States, Nigeria and South Africa.
"The community is no longer as strong: it concentrates mainly on helping the victims of the (Ergodan regime's) repression," he said.
"It's over and they know it."