Small bombs exploded at the Swiss and Russian embassies in Athens on Tuesday, a parcel with explosives was intercepted at the German chancellor's office and another package addressed to Italy's prime minister caught fire when it was checked.

The bombs may be intended to spur an anti-government vote in Sunday's local elections in protest against Prime Minister George Papandreou's austerity plan, agreed with the EU and International Monetary Fund to deal with Greece's debt mountain.

"Such brainless and irresponsible actions aim to damage the Greek people's great effort to put the country and its economy back on its feet ... they will fail, we will not bend," said Papandreou.

There have been a total of 14 actual or suspected bombs since Monday but only one casualty, a courier employee who was slightly injured when a bomb exploded in her hands.

"If there are more parcel bombs they must be abroad by now, not in Greece. Courier services have made checks and have not found anything suspect for domestic delivery," a police officer said Wednesday.

Police said members of the public had come forward with information about two men who have been arrested, while investigators searched their homes.

The ban on mail and parcel dispatches abroad is intended to give authorities more screening time. Police spokesman Thanassis Kokkalakis said authorities had given security tips to Greek courier companies to facilitate the search, and insisted that screening crews at Greek airports were fully qualified to address the issue.