ISTANBUL (Reuters) - A Turkish court ruled on Monday to keep philanthropist Osman Kavala in prison and it was expected to give a verdict next month, 4-1/2 years after he was detained, in a trial which has caused tensions between Ankara and its Western allies.

       The court had been widely expected to reach a verdict on Monday, but defence lawyers had requested more time to respond to the prosecutor's final opinion on the case and the judge set a date of April 22 for what was likely to be the final hearing.

       Kavala was detained on Oct. 18, 2017 over charges related to nationwide protests in 2013 as well as a case linked to a coup attempt in 2016. He denies any wrongdoing.

       (Reporting by Ali Kucukgocmen; Writing by Daren Butler; Editing by Ece Toksabay)