The eight packages, similar to mail bombs, were addressed to Eurogroup officials and representatives of other "economic institutions" in various European countries, a security source said.

Greek authorities were on alert after the dispatch of two parcels laced with gunpowder last week. On March 15, German authorities intercepted a book concealing explosives and addressed to German Finance Minister Wolfgang Schäuble. One day later, a second package arrived at the Paris office of the International Monetary Fund (IMF), where it exploded and injured an administrative assistant.

A source close to the investigation told Agence France Presse that the IMF mail bomb consisted of two small tubes of black powder and an electric trigger. A Greek police source said the eight packages found on Monday had been "found to contain a similar mechanism."

Far-left group responsible?

A domestic militant group known as Conspiracy of Fire Cells claimed responsibility for the first delivery to the German Finance Ministry, describing it as part of a campaign of violence by international anarchist groups. Authorities believe the far-left group was also behind the IMF letter bomb.

In both those cases, members of the New Democracy opposition conservative party were listed as senders. Police said the eight parcels discovered Monday were labeled as being sent from academic institutions.

Conspiracy of Fire Cells, which is considered a terrorist organization by the United States, sent letter bombs to European leaders - including German Chancellor Angela Merkel - and several foreign embassies in Athens in 2010. Police allege the group has carried out more than 150 criminal acts over the past several years.

nm/gsw (Reuters, AFP, AP)