Greek police detonated a parcel bomb addressed to the French embassy in Athens on Thursday but checks at a courier company on more than 20 other packages destined for embassies and ministries showed they were harmless.
The parcel bomb, disguised in a hollowed out book, was sent on Monday, when the first of a wave of devices was sent to foreign governments and embassies by what the government has described as Greek "extreme left, anarchist groups."
"Initial evidence showed the parcel was sent ... with the others (on Monday)," a police spokesman said.
A Transport Ministry source, who declined to be named, said authorities had no plans so far to extend a 48-hour suspension on air freight abroad of mail and packages from Greece imposed early on Wednesday.
However, another official said a final decision would be taken after consultation with police. The ban is set to end shortly after midnight (6 p.m. EDT).
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.
Police also intercepted a booby-trapped parcel addressed to French President Nicolas Sarkozy on Monday and found parcel bombs at the Chilean and Bulgarian embassies.
Unusual senders' details on some packages -- including the archbishop of Athens and Greece's deputy prime minister -- raised the alarm, as well as other parcels lacking the details.
"All evidence shows this is a clear domestic case, with no connection with international terrorism," Greek Foreign Minister Dimitris Droutsas said on Wednesday. "The evidence so far shows we are dealing with extreme left, anarchist groups."
There was no immediate government comment on Thursday.
The devices 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.
They did not contain enough explosives to seriously harm any recipient -- police said most burst into flames when they were opened rather than exploding in transit -- and analysts say they were likely designed as show of force by Greece's web of urban guerrilla groups.
"They did not intend to cause casualties," said George Kassimeris, senior research fellow in conflict and terrorism at Britain's University of Wolverhampton. "They want to dictate events by creating problems for the government, the security system, send a message to international actors."
Greece has a decades-old history of leftist violence. Some groups became more active after riots in December 2008 that were triggered by the police killing of a teenager and attracted worldwide media attention.
They usually target government buildings, police stations and banks, mostly at night, and make warning calls.
Two Greeks in their 20s arrested on Monday after a package exploded at a courier company in Athens, slightly injuring one employee, have been charged with participating in guerrilla groups, a court official said.
They are accused of sending parcels bombs addressed to the Mexican embassy, to Sarkozy, the Belgian embassy and to Europol.
Police carried out Thursday's controlled explosion outside a courier company, a Reuters witness said.
A police source said the bomb had been concealed in a large book. Police said the package addressed to Italy's Silvio Berlusconi was also a book containing an explosive device.
The courier had taken the parcel to the embassy but when security officials there discovered it had no sender's details, they gave it back to the courier, who informed the police.
Police checking more than 20 packages at a courier company in the Athens suburb of Markopoulo on Thursday found nothing suspicious. Police also detonated a suspicious package outside a bank, but found it contained no explosives.