Russia's Federal Security Service on Wednesday said it detained Evan Gershkovich, a Wall Street Journal reporter and a U.S. citizen, on espionage charges.

"It was established that E. Gershkovich, acting on the instructions of the American side, collected information constituting a state secret about the activities of one of the enterprises of the Russian military-industrial complex," the security agency said, as translated. 

He was detained in Yekaterinburg, a city in the Ural Mountains.

The Wall Street Journal said Gershkovich reports from the paper's Moscow bureau.