Italy's finance police said in a statement on Thursday that the weapons were found in a lorry with Dutch number plates as it crossed the border on Tuesday.
They said the lorry was headed to Belgium via Germany and the Netherlands.
Although customs rules were not violated, the Turkish lorry driver did not have licences for the pump-action Winchestor SXP guns, which were found packed in cardboard boxes.
A spokesman for Trieste police told The Local that the driver is not suspected of any wrongdoing but that a legal representative of the Turkish company which manufacturers the weapons has been reported.
Authorities in Belgium have been notified, the spokesman added.
“We're in the process of exchanging information with Belgian authorities," he said.
"At the moment, there are no more details to share. We don't know what the objective for the arms' was – we are working on finding this out."
Italy has “significantly” tightened security checks at its borders and airports in the wake of the Paris attacks earlier this month, in which 130 people died, he added.
Brussels was also put on its highest terror alert (level four) last weekend amid warnings of a “serious and imminent” threat of attack. The alert was lowered to level three on Friday.