ISTANBUL (AP) — Turkish prosecutors detained a prominent philanthropist for alleged ties to a 2016 coup attempt Tuesday night, just hours after a court acquitted him on terrorism-related charges and ordered his release from jail after 840 days.

The Istanbul prosecutor’s office said in a statement that it planned to appeal the verdict by a panel of judges that found Osman Kavala not guilty of charges resulting from anti-government protests. While the judges also set Kavala free, prosecutors ordered him to be detained in a separate investigation involving the failed coup.

Earlier Tuesday, a court in Istanbul acquitted Kavala and eight other activists of organizing or aiding the 2013 protests in an attempt to overthrow the Turkish government.

The prosecutor’s office said in a statement that he is under investigation now as a suspect in the attempted overthrow of the Turkish constitutional order through alleged links to the July 15, 2016 coup attempt.

More than a hundred supporters, among them artists, intellectuals and civil society figures, waited for hours to see Kavala walk free from a prison. The former businessman and founder of a nonprofit organization that focuses on cultural and artistic projects spent more than two years in pretrial detention.

An anxious silence took over people in the stunned crowd when word of the new investigation reached them.

In line with legal procedures for detained suspects, Kavala, 63, would be taken to a hospital for health checks, then to a police station and eventually to court for a hearing on whether he should be formally arrested or released pending trial.

Somewhat similar detention or arrest orders were issued in the cases of jailed writers and an opposition politician after courts ruled for their release from custody.

The Turkish government blames U.S.-based Muslim cleric Fethullah Gulen for the failed coup and cracked down on his alleged followers, arresting tens of thousands of people under a state of emergency. Critics have said the wide net wrongly detained or fired from public service jobs people without links to the cleric’s network.

The 2013 protests at the center of the first case were organized to oppose the planned development of a shopping mall on the site of a small park in central Istanbul. The Gezi Park demonstrations grew into a wider protest movement across Turkey.

Kavala was arrested in November 2017. He rejected the accusation that he organized and financed the protests four years earlier, saying he took part in peaceful activities to defend the environment and the park near his office.

The European Court of Human Rights ruled for his immediate release in December, saying Kavala’s extended time in custody served “the ulterior purpose of reducing him to silence” with a “chilling effect on civil society.”

The court decision to acquit him fulfilled Turkey’s obligation to implement the European court’s ruling, but observers said the new detention order and investigation of Kavala would allow Turkey to bypass the human rights court.

Emma Sinclair-Webb of Human Rights Watch described the detention warrant as “lawless and vindictive.”

Critics saw the terrorism-related charges brought against a total of 16 people as a momentous bid by those in power to crack down on opposition voices and criminalize mass anti-government protests.

More than 300 people attended the trial Tuesday, joining lawmakers, foreign delegates and rights group members at a courthouse near the Silivri maximum security prison campus. Hundreds of others waited outside.

Supporters broke into applause and tears when a judge quickly read the panel’s verdict for acquitting the nine activists instead of convicting them and imposing the lengthy sentences many had feared. The judge said Turkish authorities did not present enough “concrete and certain evidence” to convict.

“Complaints of the lawyer not being heeded by the court, statements by the defendants, really seemed to fall on deaf ears in terms of the panel of judges,” Andrew Gardner of Amnesty International said after the acquittal, describing the trial as a roller-coaster. “And then suddenly, for the judge to announce a not-guilty verdict for all, is incredible.”

The prosecutor had sought a life sentence in solitary confinement without parole for Kavala, architect Mucella Yapici and Yigit Aksakoglu, who spent 221 days in pretrial detention. They denied trying to overthrow the government and say the protests were an exercise of democratic rights.

After hearing about the new detention order for Kavala, Yapici tweeted: “Once again, a freakishness of the law, first you linked him to Gezi in an unrelated and illegal way and now July 15… Pity this country.”

An estimated 3.6 million people joined the Gezi Park protests, according to government estimates, and thousands were injured. Police used tear gas and water cannons to disperse mostly peaceful protesters and were accused of using excessive force.

The Turkish Bar Association put the number of people killed during the anti-government protests at 15, including a police officer. Prosecutors said in their criminal indictment that there were five protest-related deaths.

The discrepancy stems from the bar association’s inclusion of deaths from heart attacks and cerebral hemorrhages thought to be caused by pepper spray, as well as of people killed at other protests during the same period.

Hours after the verdict, presidential spokesman Ibrahim Kalin said of the protests: “We should never get out of our minds that the process hurt Turkey as a whole.”

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Robert Badendieck in Istanbul and Suzan Fraser in Ankara, Turkey contributed to this report.