ISTANBUL - A Turkish court detained a top media executive and three other people on Friday pending trial on accusations of belonging to a terrorist group, in a case which President Tayyip Erdogan has defended as a response to 'dirty operations' by his enemies. The executive, Hidayet Karaca, runs a television station close to the president's ally-turned foe Fethullah Gulen, a U.S.-based Muslim cleric. Erdogan accuses Gulen of seeking to topple him through supporters in the judiciary, police and other institutions.