Greek police said they found eight "suspect" packages on Monday addressed to global economic institutions, after a domestic militant group sent mail bombs to the IMF and German finance ministry last week.
The packages, intended for "officials at European countries" were located at the Greek postal service's main sorting centre north of Athens, a police statement said.
A police source later said the packages were intended for officials at the Eurogroup and other global economic institutions.
Last week, a mail bomb sent to the International Monetary Fund's offices in Paris exploded and injured a secretary. A second bomb sent to the German finance ministry was intercepted by security.
The investigation so far suggests that both the IMF and the German finance ministry bombs were sent by a far-left group called the Conspiracy of Fire Nuclei, which police thought they had mostly dismantled in 2011.
A source close to the investigation in Paris last week said the mail bomb consisted of two tubes of black powder and a makeshift electric trigger.
A second Greek police source on Monday said the eight additional packages had been scanned and "found to contain a similar mechanism."
To make the packages more likely to be opened, the perpetrators listed Greek economic officials and academics as the senders.
Last week, the names of two senior officials in Greece's conservative New Democracy party were used as the alleged senders -- deputy leader Adonis Georgiadis and party spokesman Vassilis Kikilias, formerly a police minister himself.
The Berlin package was intended for German Finance Minister Wolfgang Schaeuble, and was discovered a day before he was due to host his new US counterpart, Steven Mnuchin.
Greek authorities last week said package screening procedures at Athens airport were state of the art, while a spokesman for the airport's security company said the small quantity of gunpowder contained in the packages was hard to trace.
Conspiracy of Fire Nuclei, which is considered a terror organisation by Washington, sent mail bombs to foreign embassies in Greece and to European leaders in 2010.
The outfit, which has links to the Italy-based Informal Anarchist Federation (FAI), has only claimed last week's German finance ministry hit.
Many Greeks blame Germany and the IMF for imposing years of public-sector cuts and policy overhauls in exchange for bailout packages needed to prop up the debt-ridden country.
Police say the name "Conspiracy of Fire Nuclei" had been used as a cover by urban militants carrying out minor arson attacks against car dealerships and police vehicles since the middle of the last decade.
In 2011, several of its members, many of them very young, were convicted of "participating in a criminal organisation" and given long prison sentences.
Three years later, the group announced its return and has since been committing sporadic attacks.
The organisation denounces capitalism and consumerism, as well as police repression and worker exploitation.