ATHENS - Greece stopped all airborne parcels headed overseas and screened thousands of packages Wednesday in an attempt to stop a spate of bombings blamed on Greek militants targeting diplomatic missions and European leaders.
A 48-hour ban on all outgoing parcel deliveries abroad took effect after mail bombs reached the office of German Chancellor Angela Merkel and halted flights for hours at Italy's Bologna airport, where a package addressed to Italian Premier Silvio Berlusconi caught fire.
The attacks, which followed an unsuccessful Yemen-based mail bomb plot, highlighted the difficulty of keeping bombs out of the international delivery system. Several European governments urged vigilance but didn't say they were increasing measures already in place at leaders' offices.
Merkel, however, called for improved checks on cargo deliveries.
"This incident and the problem that we had at the chancellery with a suspect package must give cause to better co-ordinate checks on cargo inside Europe ... and then as far as possible worldwide," Merkel told the daily Passauer Neue Presse.
At least 11 mail bombs were detected in the Greek capital on Monday and Tuesday -- one addressed to French President Nicolas Sarkozy and eight to the Athens embassies of Bulgaria, Russia, Germany, Switzerland, Mexico, Chile, the Netherlands and Belgium.
Three of the bombs exploded or caught fire in Athens, causing minor damage and leaving one delivery service employee burned.
Police investigators said none of the devices examined so far contained lethal amounts of explosives -- unlike those used by the Yemeni militants.
Government spokesman George Petalotis said that the Greek mail bombs had no link to Islamist groups.
Authorities are questioning two suspects arrested Monday in connection with the bombings, and released the photographs of five other suspects believed to be associated with them. The suspects, most in their early 20s, have been linked to an anarchist militant group called Conspiracy Nuclei of Fire.
Greece has suffered a spike in militant attacks -- including a deadly letter bombing earlier this year -- since massive riots in 2008 triggered by a police shooting of a teenage boy.
The country was plagued by far-left terrorism in the 1980s and 1990s, with more than 20 people killed in gunfire and bombing attacks. Although the deadliest of these organizations were eradicated over the past decade, their attacks have inspired several small radical anarchist or nihilist groups violently opposed to capitalism and all forms of state authority.
Believed to recruit from anarchists and students who often clash with police in Greece's frequent protests, these groups have come to dominate domestic political violence in recent years. But they are seen as lacking the sophistication and tight organization of the older far-left groups.
"Clearly we are dealing with amateurs but those are amateurs who got worldwide attention," said Greek terrorism expert Mary Bossi. "The suspects are all young but I have some reservations on who might be guiding them."
Prime Minister George Papandreou said the government would be "unyielding" in its pursuit of the bombers, whose attacks he linked with the debt-ridden country's financial woes.
"Democracies cannot be terrorized," Papandreou said. "These irresponsible and mindless acts were intended to harm the Greek people's huge effort to set the country to rights, to set the economy on its feet and for the country to regain its credibility. They will not succeed. We will not succumb."
But terrorism experts say Greek police face a difficult task in trying to shut down the mail bombing campaign.
"It's very difficult to prevent the initiation of this kind of attack ... The initiative lies with the people who want to mount the attack, not with the authorities," said Michael McKinley, a senior lecturer in International Relations at the Australian National University in Canberra.
McKinley said fully screening all mail would "bring the Greek postal system to a halt" while catching the five remaining suspects might not stop the problem.
"It depends how many committed people are following them," he said. "I most cases of homemade explosives, the people involved are not very expert. So effectively this problem when you have an open society: If people are determined to cause a problem they can do."
Also Wednesday, police said 11 cars were burned in overnight arson attacks, most using small cooking gas canisters, including eight vehicles owned by the state electricity company.
