Close cooperation between Italy and Tunisia had enabled the Italian authorities to identify a “small number” of Tunisians with extremist sympathies but they had all been repatriated, the official said.
Interpol would not comment directly on The Guardian’s claims.
“When member countries share information via Interpol, it remains under their ownership and we cannot comment without their approval,” the agency said.
“Interpol regularly sends alerts and updates to its 192 member countries on wanted terrorists and criminals via our secure global police communications network.”
Some Italian security analysts were doubtful about the story.
“Terrorists never arrive in migrant boats – no serious terrorist organisation would take the risk of putting their trained people on board an unsafe boat which risks capsizing when hit by the first big wave,” Andrea Margelletti, president of the Centre for International Studies, told the Italian news agency Adnkronos.
“ISIS could use reliable, privately-owned vessels in order to ensure a safe crossing over to Italy,” said Mr Margelletti, a strategic adviser to the Italian defence ministry.
“But then there is another question – how do these terrorists, who don’t speak any Italian, find places to stay, how do they eat, without a very strong logistical support network, which our police and intelligence agencies have not found. Those agencies are among the best in the world and they are very capable when it comes to counter-terrorism.”