Tunisian authorities on Tuesday denied accusations by Italy that migrants it arrested as they tried to cross the Mediterranean for Italian shores were "terrorists".

Tunisia's interior ministry on Monday announced the arrest of 15 people heading for European shores, stating that nine of them were considered by police as "Salafists", or fundamentalist Muslims.

On Tuesday Italian Interior Minister Matteo Salvini tweeted about the arrest of nine "ISLAMIST EXTREMISTS" attempting to travel to Italy, saying: "That's for those who say 'terrorists don't arrive by boat.'"

Salvini, who is also leader of the far-right League Party, in March described migrants arriving illegally to Italy as "delinquents".

Reacting to Salvini's tweet, spokesman for Tunisia's National Guard Houssemeddine Jebabli told the country's Mosaique FM radio that "there was no terrorist project against Italy in this attempt to migrate illegally".

"They wanted to flee Tunisia in search of a better life, like other migrants," Jebabli told AFP, adding that those arrested were men aged 28 to 42 and that none of them were suspected of having links to terrorist groups.

A growing number of Tunisians seeking a better future are trying to cross the Mediterranean and enter Europe illegally.

In the first half of 2018, Tunisian authorities arrested 2,659 people for trying to cross the sea illegally, compared to 564 people during the same period last year.

Hundreds have drowned in a series of deadly shipwrecks in recent months - that latest on June 3 left 87 people dead.

Separately on Tuesday, the interior ministry announced the arrest of two youths suspected of having received training over the internet from Islamic State group jihadis on how to make explosives and carry out knife attacks.