Greek police said Friday they are investigating a threat to Yorgos Provopoulos, the country's central bank governor, after an envelope containing two bullets was sent to his office.

Politicians, state officials, police officers and representatives of the business world have often been targeted by anarchist guerrilla groups in Greece for years and attacks have spiked amidst the debt crisis, Xinhua reported.

Earlier this week, arsonists targeted the office of Interior Minister Yannis Michelakis in Athens causing minor damage.

Last year, Finance Minister Yannis Stournaras received a similar envelope with a bullet.

Authorities are on high alert after the recent escape of a convicted terrorist during parole from prison during the holiday season, fearing more serious attacks.

In December last year, a group of armed assailants fired with automatic rifles at the German ambassador's residence in Athens, causing material damage.