Italian police arrested five Tunisians as part of a major operation against suspected supporters of Islamist terrorism in central and southern Italy.
The swoop is the latest in a series of similar raids this month, coming as Italy steps up the number of foreigners it expels.
On Wednesday anti-terrorism police arrested an Italian citizen of Moroccan origin who they said was an Islamic State sympathiser planning a truck attack.
“A vast anti-terrorism operation” was being carried out by special investigation forces based in Rome and nearby Latina, police said in a statement.
The five Tunisians detained are suspected of being part of a network connected to Anis Amri, the Tunisian who killed 12 people when he drove a truck into a Christmas market in Berlin in December 2016, judicial sources told Reuters.
Amri was shot dead by Italian police near Milan four days after the Berlin attack.
Prosecutors suspect the arrested Tunisians of crimes including planning international terrorism, falsifying documents and helping illegal immigration of radicalised Tunisians, the sources said.
Sources said there was no evidence the suspects participated directly in the Berlin truck attack or were preparing any imminent attack in Italy.
As part of their operation, police were carrying out searches in Rome, the port city of Naples and central and southern towns Latina, Viterbo, Caserta and Matera, the sources said.
Interior Minister Marco Minniti said the security threat to Italy from Islamic State supporters was higher than ever because more foreign fighters were attempting to return to Europe via Italy after the jihadist group suffered defeats in Syria and Iraq.
To date this year, 29 foreigners, mostly Muslims, have been expelled from Italy as suspected threats to national security.