ISTANBUL (Reuters) - A Turkish court on Friday kept in jail the philanthropist Osman Kavala, who has denied charges of involvement in an attempted 2016 coup and has already been detained more than three years without conviction in what critics call a silencing of dissent. The interim ruling of the Istanbul court, which was crowded with observers including foreign diplomats and opposition politicians, scheduled Kavala’s next hearing for February 5 and will hear another witness. Ankara’s Western allies have raised concerns about Kavala’s detention and the European Court of Human Rights has said it only serves to silence him. After President Tayyip Erdogan last month promised judicial reforms, rights activists redoubled calls for his release. After the ruling, Emma Sinclair-Webb of Human Rights Watch called Kavala a “political hostage” to a “show trial” with little evidence. “It is an absolutely shocking misuse of the Turkish justice system and it discredits the country,” she said. Immediately after he was acquitted in February of charges related to nationwide protests in 2013, Kavala was arrested again - on charges related to the failed 2016 coup. Critics say the detention points to political pressure on Turkey’s judiciary, which they say has been bent to punish thousands of the government’s perceived opponents since 2016. Erdogan’s reform pledges have prompted speculation that Kavala and others may be released, but the president said last month he could never defend the philanthropist and called him the sponsor of the Gezi Park protests in 2013 - despite courts clearing him of that accusation. VIDEO LINK Kavala, 63, told the court via video link from prison that none of the charges are based on “facts, evidence or objective evaluation of a concrete criminal act”. The allegations “are in stark contrast to my world view, ethical values and the goals of the projects carried out by the civil society organizations under my supervision,” he said. His jail time was “mental torture,” he added as his wife listened among a crowd that spilled out of the court and into the hallway. The new indictment accuses Kavala of collaborating with Henri Barkey, a prominent U.S.-based Turkey scholar. It accuses Barkey of links to the network of U.S.-based Turkish Muslim cleric Fethullah Gulen, which Ankara says orchestrated the coup attempt. Gulen denies involvement. Kavala and Barkey are charged with attempting to overthrow the constitutional order, which carries a life sentence without parole, and with espionage, which could lead to 20 years in jail. Barkey says the charges are a “complete fabrication”. The indictment says Kavala and Barkey spoke by phone nearly three months after the July 15 2016 failed coup; that they met at an Istanbul restaurant on July 18 of that year; and that signals on their phones came from the same area many times in the preceding few years. Barkey told Reuters by email in October that the two ran into each other at the restaurant and chatted briefly. He said their phones could have been in the same area of a crowded city at other times without them meeting. Opposition CHP lawmaker Sezgin Tanrikulu, who attended the hearing, said afterwards any judicial reforms by Erdogan’s government “would be meaningless if this mentality stays the same”.