Amnesty International campaigners hold masks of Turkish rights activist Taner Kilic during a demonstration in Berlin in 2018.
Istanbul, Turkey CNN  — 

A Turkish court sentenced four Amnesty International activists to between two and six years in prison on terrorism charges in a high-profile trial Friday, which the human rights group described as a “travesty of justice of spectacular proportions.”

The honorary chair of Amnesty International Turkey, Taner Kilic, was sentenced to six years and three months in jail for being a member of terror organization, while the group’s former director İdil Eser was sentenced to two years and one month for aiding a terror organization.

Amnesty members Günal Kursun and Özlem Dalgiran were also given two years and one month sentences for aiding a terror group.

The human rights group denies all the charges and said that every allegation against its members has been “comprehensively exposed as a baseless slur.”

Amnesty International Turkey's Honorary Chair, Taner Kilic, pictured during a speech in Istanbul, 2018.

Another seven defendants were acquitted. The 11 human rights activists were arrested and charged in the summer of 2017 on terrorism charges.

The defendants have the right to appeal to the Court of Appeal, which Amnesty Turkey tweeted that they will use. “As we said before the trial, we will not accept even one of our friends to be sentenced. We will continue to follow the case through higher courts,” it said.

The four activists will not be imprisoned pending their appeals. The appeal process could take months or years.

Andrew Gardner of Amnesty International said in a statement: “Today, we have borne witness to a travesty of justice of spectacular proportions. This verdict is a crushing blow not only for Taner, Özlem, İdil and Günal and their families but for everyone who believes in justice, and human rights activism in Turkey and beyond.”

Amnesty International Turkey's former director Idil Eser, pictured in 2017, was sentenced to jail for aiding a terror organization.

“The decision of the court is staggering. During 12 court hearings, each and every allegation has been comprehensively exposed as a baseless slur. The court’s verdict defies logic and exposes this three-year trial as the politically motivated attempt to silence independent voices it was from day one,” Gardner added.

The most high-profile member of the group, Kilic, was accused by the prosecutor of being a member of the cleric Fethullah Gulen’s network, which Turkey’s government deems a terrorist organization.

Kilic denies being a member of the organization, headed by the US-based preacher Gulen, who Turkey blames for masterminding the 2016 coup attempt during which around 250 people died.

Kilic was also accused of downloading a messaging app called ByLock used by the organization, which he denies.

The other 10 defendants, including Amnesty International Turkey’s former director Eser, were arrested separately at a hotel on the island of Büyükada, off the coast of Istanbul, where they were attending a digital security workshop.

They were accused of taking part in a secret meeting, directed by Kilic, in a case locally dubbed the “Büyükada trial,” according to Amnesty International.

According to Human Rights Watch, “terrorism charges continued to be widely used” since the failed coup attempt and many terrorism trials in Turkey “lack compelling evidence of criminal activity.”

The practice of holding individuals charged with terrorism offenses in prolonged pre-trial detention “raised concerns its use has become a form of summary punishment,” it said.

Anti-goverment protesters unfurl the Turkish national flag in Gezi Park in June 2013.

It is Turkey’s second recent court case involving prominent rights activists, turning a spotlight on the country’s continuing detention of campaigners more than three years after 2016’s attempted coup.

The verdict comes just months after the prominent philanthropist, Osman Kavala, was given a brief taste of freedom when he was acquitted over 2013 protests in Istanbul’s Gezi Park – and then hours later re-arrested for alleged links to the coup.

Kavala was one of several activists acquitted over their involvement in the Gezi Park protests seven years ago, which began over a plan to turn a small park in central Istanbul into a shopping mall. The demonstrations quickly morphed into larger anti-government rallies across Turkey.

But the celebrations for the acquitted activists were short lived, after prosecutors announced Kavala would remain in detention.

Milena Buyum, Amnesty International’s Turkey campaigner, said in a statement that the decision smacked of “deliberate and calculated cruelty.”

Isil Sariyuce reported from Istanbul. CNN’s Sheena McKenzie and Emma Reynolds wrote from London. CNN’s Jomana Karadsheh and Yusuf Gezer contributed to this report