Greek police said on Tuesday the country's civil aviation authorities were suspending all deliveries of mail and parcels abroad for 48 hours.
A police statement says the freeze will allow authorities to check for the existence of more mail bombs. The decision comes after a wave of mail bombs were sent to foreign embassies in Greece and to German Chancellor Angela Merkel's office.
Late on Tuesday, police said a suspicious package addressed to Italian Premier Silvio Berlusconi found on board a private mail courier company plane was being examined at Bologna airport.
Greek anarchist extremists are suspected of mounting the attacks, and two Greek men were charged Tuesday with sending mail bombs.
They were allegedly carrying mail bombs addressed to French President Nicolas Sarkozy and the Belgian Embassy, along with handguns and bullets. One wore body armour, a wig and a baseball cap.
Police detonated the bombs along with a fourth device found at a delivery company and addressed to the Dutch Embassy.
The explosions in Greece continued on Tuesday with the detonation of a bomb outside a six-story building that is home to the Swiss Embassy.
Soon after, a courier heading for another embassy became suspicious about a package and stopped at Parliament, where police explosives experts detonated a bomb.
Police then found explosive devices at the Bulgarian Embassy and a central Athens courier company, where the German embassy had returned a suspicious package, and set them off in controlled explosions.
A fifth bomb went off on the grounds of the Russian Embassy.
Authorities closed down sections of the capital and checked dozens of potential targets, and all embassies were
given additional police security.
Late on Tuesday, police said that they had also destroyed two suspicious packages at Athens International Airport.
The controlled detonations occurred in the airport's cargo area and did not affect flights.
Authorities did not immediately confirm a report by Greek state television that the two destroyed packages were bound for The Netherlands and Luxembourg.
Meanwhile German police in Berlin also disarmed a potentially harmful package from Greece at Chancellor Angela Merkel's office on Tuesday.
Merkel's spokesman Steffen Seibert said the suspicious package intercepted in the mailroom of her office was personally addressed to the German chancellor.
German Interior Minister Thomas de Maiziere said the package, which arrived midday at the mailroom of Merkel's office, was sent from Greece two days ago and resembled the other mail bombs in Athens.
Merkel was in Belgium when the package arrived.