A Turkish court acquitted leading civil society figures, including rights defender Osman Kavala, on Tuesday in a highly controversial trial over the anti-government "Gezi Park" protests of 2013.
The judge said there was "not enough concrete evidence" that Mr Kavala and the other 15 defendants sought to overthrow the government.
Seven of the defendants, who remain on the run, were not formally acquitted.
Protesters during a rally against the government's crackdown on environmentalists angered by a development project at the Gezi park, Turkey in 2013. Source: AAP
Mr Kavala, who spent more than 800 days in pre-trial detention and faced a life sentence without parole if convicted, became a symbol of what critics say is a crackdown on civil society under President Recep Tayyip Erdogan.
He received loud cheers as he left the packed courtroom in Silivri, on the outskirts of Istanbul.
Prosecutors accused the group of orchestrating the mass protests of 2013 that began over plans to demolish Gezi Park - one of the only green spaces in Istanbul's centre - but quickly spiralled into broader demonstrations against Erdogan, then prime minister.
Critics have called the trial "a mockery of due process" in which the prosecution failed to present any evidence of wrong-doing by the defendants.
"This is a trial that should have never happened in the first place. This whole process has caused untold misery to those who were so wrongfully targeted," Emma Sinclair-Webb, of Human Rights Watch, told AFP at the courthouse.
Family members and friends celebrate after a court acquitted nine leading Turkish civil society activists of terrorism-related charges, including Osman Kavala. Source: AAP
'Conspiracy theory'
Andrew Gardner, of Amnesty International, said the verdict was "obviously fantastic news" but warned against too much optimism.
There are "countless other trials of journalists, of opposition political activists, of human rights defenders. The justice system is completely devoid of independence and impartiality in Turkey," he told AFP.
In December, the European Court of Human Rights heavily criticised the quality of the Gezi Park prosecution.
It ruled that the 657-page indictment against Kavala lacked "facts, information or evidence" to raise even the suspicion that he helped organise the protests, let alone attempted to overthrow the government, and called for his immediate release.
"The bill of indictment… set out a conspiracy theory, devoid of ascertainable facts," it said.
Mucella Yapici, one of 16 defendants, greets to her supporters after the court's verdict in front of the Silivri courthouse in Istanbul. Source: AAP
The Turkish court still put Mr Kavala and the other defendants through two more hearings in December and January.
The verdict was welcomed by several foreign observers, including the US embassy in Ankara and the Council of Europe, a 47-nation body overseeing human rights, of which Turkey is a member.
"Free speech, the right to organise non-violent protests and the right to liberty are basic human rights in all Council of Europe member states," the council said in a statement.
Among the criticisms of the trial was the fact that defence lawyers were denied the chance to cross-examine the key government witness, identified as Murat Papuc, when he gave evidence in December after he claimed his life was in danger.
Lawyers also decried the inclusion of testimony from a police officer convicted of kicking a Gezi Park protester to death in July 2013, who now portrays himself as a victim of the demonstrations.
The defendants received support from Ekrem Imamoglu, the new high-profile mayor of Istanbul who took control of the city out of the hands of the ruling party last year.
"The acquittal of all the defendants in the #GeziPark trial is a true source of joy, and restores trust in the Turkish judicial system. I salute all those who stand to defend our city's history, culture and nature," he tweeted.
Mr Kavala's supporters say he was targeted because he worked to build bridges across Turkey's often fractious ethnic and social divides, in contrast to the combative rhetoric favoured by Erdogan's ruling party.
As chairman of the Anatolian Culture Foundation, which promotes human rights through art, Kavala even sought to build ties with neighbouring Armenia, with which Turkey has no diplomatic relations.
