A little known group called the Informal Anarchic Federation has claimed responsiblity for the embassy bombings in Rome that come as U.S. cities are already on a heightened state of alert going into the Christmas holiday.
According to the Italian news service ANSA, the claim was found in a small box found next to one of the injured employee workers. There appears to be a link between this morning's bombings and package bombs sent to embassies in Athens in November.
Italian news reports say the claim found today read in Italian, "We have decided to make our voice heard with words and with facts, we will destroy the system of dominance, long live the FAI, long-live Anarchy."
The note appeared to be typed on a computer and was folded a number of times inside a box of mints, according to reports.
Bombs exploded at the Swiss and Chilean embassies, according to police, and a similar suspicious package was sent to the Ukrainian Embassy but proved to contain no explosive material.
According to investigators, the signature on the claim proves the links between the Italian and Greek insurrectionists.
The explosions have put security efforts worldwide on high alert, including New York City, where Police Commissioner Ray Kelly said officials are "on alert" going into the holiday weekend.
"Quite frankly there is always a possibility of an attack here," said Kelly. "We are on the top of the terrorist target list. That is the world in which we live."
"This is not new news for us, the fact that there may be something happening or planned to happen, we have no specific information," he said. "But we are on alert, we are watching indicators we normally watch."
Kelly added that the investigation into the Rome bombings is leaning toward it being a "product of the anarchist community."
Federal authorities will on watch over the coming days, sources tell ABC News, ever-mindful of last Christmas' nightmare with the so-called underwear bomber.
Shoppers searching for last-minute gifts are also likely seeing lots of additional police on public transportation as a precaution.
All embassies and consulates in Rome are being checked for suspicious packages. No explosive material has been detected in mailrooms at the United Kingdom, United States, Israeli, German or French embassies in Rome. But all embassies are intensifying their security.
"We are in the process of reminding all U.S. embassies worldwide to review current mail screening procedures and to continue vigilance when opening mail," a U.S. State Deptartment official told ABC News.
The explosion at the Swiss Embassy badly injured a mailroom employee, sending him to the hospital. The 53-year-old is in danger of losing his left hand, and is being operated on at Policlinico Umberto I Hospital.
''We express total solidarity with the Swiss embassy and all its personnel, who have been subject to a deplorable act of violence that deserves our firmest condemnation,'' said Italian Foreign Minister Franco Frattini, according to The Associated Press.
The package delivered to the Chilean Embassy, addressed to the cultural office, was in an envelope identical to the one delivered to the Swiss Embassy. One person at the Chilean Embassy was injured, according to ANSA. The parcels were each about the size of a videocassette, sources told ABC News.
It wasn't immediately clear why these embassies were targeted. "We still don't know the origin or the cause of the attack, nor where the envelope was sent from," said the Chilean Foreign Minister in Santiago, Alfredo Morena.
Tension is thick in Rome and across Italy because of terror worries, government cuts and student protests over education reforms.
The explosions occurred only two days after a terror scare on Tuesday. A device suspected of containing explosive powder was discovered Tuesday in Rome's subway system, but was a "fake," the city's mayor said.
"The device could not have exploded," mayor Gianni Alemanno said, according to AP. Alemanno said the package was "a fake."
One Italian news service said the device, which contained a powdery substance initially thought to be an explosive, was left in a grocery bag underneath a seat and was spotted by a conductor, the AP reported. The stop, which is located on the outskirts of Rome, was evacuated.
Across Europe, like the United States, there is a growing concern about terror attacks this holiday season in the form of suicide bombers or Mumbai style attacks.
On Monday, 12 men were arrested in the United Kingdom as they were allegedly in the final stages of a major bomb plot targeting several cities there.
The men were arrested after weeks of surveillance by law enforcement and MI5 in raids in London, Cardiff, Birmingham and Stoke-on-Trent. The men are between 17 and 28 years old and are mostly British citizens from Bangladeshi and Pakistani backgrounds.
"The arrests were absolutely necessary to keep the public safe," John Yates, assistant commissioner of the Metropolitan Police and Britain's senior counterterrorism police officer, said Monday of the U.K. arrests. He also reminded people to remain vigilant due to a large number of terror threats that officials are currently monitoring.
Authorities did not say the plot was timed for the holidays, but they did feel it was necessary to act right away, an indication this plot was in its final stages. The arrests were the biggest anti-terror action in Britain since April 2009, when another dozen men were detained in Manchester in connection with an alleged Al Qaeda bomb plot.
On December 11, there was a failed attack in Stockholm, Sweden, where a suicide bomber entered a square and blew himself up, injuring two other people.
Last month, parcel bombs were sent to several embassies Athens, Greece. The Swiss, Russian, German, Bulgarian and Chilean embassies received packages, and other parcels were addressed to the Mexican, French, Belgian and Dutch embassies. All contained crude devices and caused little or no damage.
Phoebe Natanson contributed to this report from Rome, Italy.