ATHENS (Reuters) - The European Central Bank and two senior euro zone officials were among the intended targets of booby-trapped packages intercepted by Greek authorities on Monday, security sources said on Tuesday.

A slogan reads " The poor vote for NO" next to a mailbox outside a closed Hellenic Post branch in Athens, Greece, March 20, 2017. REUTERS/Alkis Konstantinidis

Packages containing small amounts of explosive material were delivered to the International Monetary Fund in Paris and the German Finance Ministry last week, sent from Greece.

On Monday Greek authorities said they had discovered eight more packages at a sorting center in Athens, caught on security scanners and by sniffer dogs.

In addition to an unspecified ‘regional office’ of the ECB, authorities found a package addressed to Klaus Regling, head of the European Stability Mechanism, and Jeroen Dijsselbloem, head of the euro zone group of European finance ministers.

“They were being sent to eight different countries,” one security source said.

All three European institutions are involved in financial assistance programs for crisis-hit Greece. The country has required three bailouts in return for deep economic reforms since 2010, triggering years of recession and austerity policies and pushing tens of thousands of Greeks into poverty.

A Greek urban guerrilla group, Conspiracy of Fire Cells, had claimed responsibility for the first suspect package sent to Germany and intercepted at the German finance ministry before it was opened on March 15.

It has not claimed responsibility for a letter to the IMF that exploded on March 16, but authorities assume the same group is behind it. An administrative assistant at the IMF was injured opening the package.

The undelivered packages found during a screening process at a sorting center were being examined for fingerprints and genetic material.

Conspiracy of Fire Cells first carried out arson attacks in 2009. The following year it claimed responsibility for sending 14 letter bombs to embassies in Greece and to European leaders.