Rome (CNN) -- An anarchist group claimed credit for a pair of mail bombings Thursday at embassies in Rome, vowing in messages that it plans more such acts to "destroy the systems of domination," the state-run ANSA news agency reports.

Police said that the Informal Federation of Anarchists -- an offshoot of the Italian Anarchist Federation, or FAI -- claimed responsibility for attacks at the Swiss and Chilean embassies.

Computer-written notes were sent in small boxes along with both package bombs, according to ANSA. The messages read: "We have decided to make our voices heard again, in words and deeds. We will destroy the system of domination. Long live FAI. Long live anarchy."

The notes also referenced Lambros Fountas, who was shot dead last March while protesting in Athens. The 35-year-old has since become a martyr for the international anarchist movement, particularly groups in Greece, Italy and Spain.

Formed in 1945, Italian Anarchist Federation had seen a "a slow but constant increase" of supporters in recent years, said the website of an umbrella group, L'International des Federations Anarchistes.

The Italian organization aims for "radical change" in support of "oppressed and exploited peoples," doing so with opposition to political powers and even the Catholic Church, the website said.

There was no warning before a Swiss-born, 53-year-old mailroom worker was seriously hurt by an explosion while opening a package at the Swiss Embassy, according to police and the Swiss Foreign Ministry in Bern. One person was taken to a hospital when the second bomb exploded shortly afterward at the Chilean Embassy, police said.

Italian Foreign Minister Franco Frattin called the attacks "a serious threat against foreign embassies in Rome." He said that authorities were checking all embassies in Rome and Italian embassies aboard for suspicious packages.

"We should avoid being alarmist," Frattin said.

Italian Interior Minister Roberto Maroni said the incident is similar to a wave of letter bombs sent last month by an anarchist group based in Greece and claimed the bombs came from there.

But Greek officials disputed the notion that anyone in their country was involved in the blasts.

"There is no evidence that the bombs originated in Greece," Foreign Ministry spokesman Grigoris Delavekouras said.

In addition to the Swiss and Chilean blasts, a "suspicious package" was found at the Ukrainian Embassy in the Italian capital, police said, but it turned out not to be dangerous. There were also false alarms at the Slovenian and Estonian embassies.

Police began their sweeps of all embassies and consulates after the blasts, the Italian ministers said. Many countries have two diplomatic missions in the city -- one to the Italian state and a separate one to the Vatican.

Security around Rome was tight Thursday night, with barriers erected at embassies and some streets closed for enhanced protection.

Bomb threats were also phoned in to City Hall and to another government office in Rome, the mayor's office said. No bombs have been found in either location.

In November, police discovered 14 parcel bombs emanating from Greece, most of which were sent to various embassies in Athens.

Police intercepted and destroyed most of them in controlled explosions, but a woman at a courier office was wounded by one of the devices and another device exploded in the courtyard of the Swiss Embassy.

Other parcel bombs were addressed to European targets including the leaders of Germany and Italy.

Two men accused of participating in the bombings were remanded into custody after they were arrested in Athens in possession of two parcel bombs, Glock pistols, a bulletproof vest and a wig.

Panagiotis Argyrou, 22, and Gerasimos Tsakalos, 24, were also in possession of a delivery slip for another parcel containing an explosive device that had been delivered to a courier service and was addressed to the Dutch Embassy, police said.

Hellenic Police spokesman Maj. Athanasios Kokkalakis called the two suspects "important members of a terrorist group."

Before the attacks, Argyrou already faced an arrest warrant alleging his membership in an illegal organization called the Conspiracy of Cells of Fire.

Greek authorities stressed that they believed the wave of letter bombs in November was the work of a home-grown Greek terrorist group that does not have ties to international organizations like al Qaeda.

Journalists Livia Borghese and Barbie Nadeau in Rome and CNN's Laura Perez Maestro in London and Joe Sterling in Atlanta contributed to this report.