ROME (Reuters) - Italy on Thursday arrested five men in an operation against suspected supporters of Islamist terrorism, police said, after tracing the phone contacts of the Berlin truck attacker shot in Milan in late 2016.

Suspected supporters of Islamist terrorism are seen in this picture released by Italian Police in Rome, Italy, March 29, 2018. Italian Police press office/Handout via Reuters

Four of the men, all Tunisians, were arrested on suspicion of conspiring to aid illegal immigration, while a fifth man, who is also believed to be Tunisian, was picked up for allegedly plotting militant attacks, prosecutor Sergio Colaiocco said.

While the suspects played no part in the December 2016 truck attack in Berlin that killed 12 people, police discovered them by following the telephone records of Anis Amri, the Tunisian man shot dead near Milan four days after the assault on the Christmas market.

“No link at all has been found” between the men and the Berlin attack, said Walter Dian, an anti-terrorism police official from Latina, a city south of the capital.

Instead, police said Amri may have been heading south to acquire false documents from them.

Amri was brought to Italy after being rescued at sea from a migrant boat in February 2011, and he later spent almost four years in prison in Sicily for vandalism, threats and theft. In 2015, he was released and told to leave the country. He went to Germany.

“There’s no concrete evidence that leads us to think a specific attack was planned, but there is enough proof for us to think that this was where things were heading,” Colaiocco told reporters, referring to the man arrested on terrorism charges.

He had consulted the Internet on how to use a missile launcher, and he had looked into the cost of renting a pick-up truck as well, the prosecutor said.

Italy has already expelled other three men tied to Amri on evidence that they had become radicalized Islamists amid a general increase in expulsions over the past year.

As part of their operation, police were carrying out searches in Rome, the southern port city of Naples and the central and southern towns of Latina, Viterbo, Caserta and Matera, investigators said.

Thursday’s sweep is not connected to a series of similar raids this month, police said.

On Wednesday anti-terrorism police arrested an Italian citizen of Moroccan origin who they said was an Islamic State sympathizer planning a possible truck attack.

Interior Minister Marco Minniti said on Wednesday 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.

So far this year, 29 foreigners, mostly Muslims, have been expelled from Italy as suspected threats to national security.