ROME  Parcel bombs exploded in the hands of employees at the Swiss and Chilean Embassies in Rome on Thursday in coordinated attacks that the authorities said were the work of Italian anarchists.

The explosions came at a time of heightened tensions, with Europe on high alert for a possible attack by Islamic terrorists and Rome on edge after the police discovered a rudimentary explosive device in the subway this week. They also followed student protests here last week that turned violent and came as the government of the Italian prime minister, Silvio Berlusconi, appeared poised to collapse.

As embassies across Rome stepped up security, an Italian anarchist group claimed responsibility for the attacks, the police said. Earlier, Italy’s interior minister said an initial investigation indicated that the bombs might have been the work of anarchists.

The police said that the “Informal Anarchic Federation” left a note at the Chilean Embassy saying it was behind the attack; other officials said the same group had claimed responsibility for the Swiss Embassy parcel bomb. The message from the group, also known as FAI, read: “We decided to make our voice heard once more with words and with acts. We will destroy the power structure. Long live the FAI, long live anarchy.”