German prosecutors say authorities have arrested a 54-year-old Swiss citizen on suspicion of espionage.

Federal prosecutors say the man, identified only as Daniel M. in line with German privacy rules, was detained Friday in Frankfurt, the country's financial capital, on the basis of an arrest warrant issued Dec. 1.

Prosecutors say M. is "suspected of working for the intelligence agency of a foreign power since the start of 2012."

They didn't identify the country he allegedly worked for.

Prosecutors say the man will appear before a judge Friday.