Italy says a Tunisian man who was sent back home after serving a seven-year prison term on terrorism charges returned to Italy on a migrant boat.

The case of Mehdi Ben Nasr is significant because right-wing, anti-immigrant politicians have long warned that extremists could blend in with the boatloads of migrants arriving on Italian shores.

The Interior Ministry said Tuesday that Ben Nasr arrived in Lampedusa, Sicily on Oct. 4 and was expelled again a week later.

He had been convicted in Italy for being part of a network of Islamic extremists who recruited fighters to go to Iraq.

After completing his sentence in April 2014, he was sent back to Tunisia, only to return 18 months later aboard a migrant boat, the ministry said.