Bucharest, Romania (CNN) -- Romania has declared a Russian diplomat "persona non grata" and has asked the diplomat to leave the country within 48 hours, a press release from the Romanian Foreign Ministry said Tuesday.
The Russian is a first secretary-level diplomat based at the embassy in Bucharest, it said.
The expulsion comes a day after the Russian Foreign Ministry branded an equivalent-stature Romanian diplomat "persona non grata" and ordered the Romanian to leave Russia within 48 hours.
Russian officials said Monday they had caught Gabriel Grecu "red-handed ... attempting to obtain secret military information."
In a statement released to Russian news agencies Monday, the Federal Security Service said it detained Grecu while he was attempting to obtain secret defense information from a Russian citizen on August 16. Spy gadgets seized from the agent fully revealed his hostile activities against Russia, the FSB said.
The Russian Foreign Ministry protested to Romanian officials Monday through diplomatic channels about Grecu's activities, which they felt were incompatible with his diplomatic status, according to the ministry's website.
The FSB said Grecu worked at the Romanian Embassy in Moscow, Russia, under the cover of the first secretary in its political department and had been an officer at the Romanian External Information Service.
The Romanian Foreign Ministry said Tuesday that it regretted that Grecu was declared "persona non grata." The Ministry representatives said that he would be withdrawn from Russia to Romania within the specified period of time.
Journalist Cosmin Stan contributed to this report.