ISTANBUL (Reuters) - A Turkish court ruled on Friday to keep philanthropist Osman Kavala in prison, after four years in detention without conviction, in an ongoing trial which has further strained ties between Ankara and its Western allies.

       Kavala was detained in October 2017 and jailed on accusations of attempting to oust the government by force. The case has been criticised as politically motivated and symbolic of a crackdown on dissent under President Tayyip Erdogan.

       (Reporting by Ali Kucukgocmen and Tuvan Gumrukcu; Writing by Dominic Evans; Editing by Daren Butler)