Two suspected letter bombs have been sent to the European police body Europol and European Central Bank head Jean-Claude Trichet, officials say.
Bomb experts on Monday defused a bomb in a package sent to the Europol headquarters at The Hague.
Hours earlier police in Frankfurt, Germany found a possible parcel bomb that had been sent to Mr Trichet.
On Sunday European Commission head Romano Prodi escaped unharmed when a parcel bomb exploded at his home.
An anarchist group said it was behind two other explosions in rubbish bins near Mr Prodi's home in the past week.
Originally posted by THENEO
There are numerous people that would like to do this so it would be difficult to know for sure who did.
Another suspect letter bomb surfaced later on Monday at the headquarters of the EU's police agency, Europol, in the Netherlands, but was intercepted by staff and defused by bomb squad officers before it caused any damage.
A meager clue came with the letter addressed to Trichet, which a police spokesman said was apparently sent from Bologna where Prodi lives.
A letter bomb has been delivered to the headquarters of EuroJust, the EU agency co-ordinating the fight against crime.
The device, which did not explode, was the fourth letter bomb delivered to a European figure in the past three days