ISTANBUL—An American pastor detained in Turkey for nearly a year on terrorism-related charges faces new charges including espionage, in a widening case that has become a top priority in Turkey for the Trump administration.

Andrew Brunson, a Presbyterian minister who had lived and preached in Turkey for two decades before he was detained last October, faces four new charges, according to people familiar with his case and Turkish state media.

Turkey’s state-run news agency reported the new charges against Mr. Brunson late Thursday. They include “gathering state secrets for espionage, attempting to overthrow the Turkish parliament and government, and to change the constitutional order,” Anadolu Agency said. Mr. Brunson has denied the charges, the news agency reported.

The new developments came just as President Recep Tayyip Erdogan increased his control over Turkey’s main intelligence agency in a decree published early Friday. The decree further consolidates government control under the state of emergency in effect since last year’s failed coup.

Mr. Brunson was initially detained last October without charge, swept up in a broad government purge of public officials and civil society in Turkey following a summer coup attempt last year.