The hold-up was filmed by passing motorists on their phones.
“Look, look, look, look … They are robbing the van, look,” said one, who caught on film the moment that the back of the security van was blown off.
The hold-up took place on Monday morning on a stretch of motorway between the cities of Lecce and Brindisi in the southern region of Puglia, which is popular with tourists during the summer months.
Members of the public called the police to say they had seen two men flee the scene at high speed in an Alfa Romeo.
The police managed to intercept the car and arrest the two men near the town of Squinzano. Police are hunting for the rest of the gang – around six men are believed to have taken part in the raid.
The authorities closed a section of the motorway in both directions while they carried out investigations.
The assailants are believed to come from Foggia, a town in Puglia which has established a notorious reputation for being the home turf of armed gangs who regularly hold up security vans.
Nicola Magno, the secretary general of a police officers’ union, expressed “deep concern for the dangerous escalation of criminal activities and the risks faced on a daily basis by members of the Carabinieri”.
He said: “Once again, Carabinieri officers find themselves on the front line of a criminal action that is extremely violent and well organised.
“The fact that a patrol was targeted with shots shows the high level of risk that our officers are being exposed to on a regular basis.
“It is only thanks to the professionalism, cool heads and sense of duty of our colleagues that we are not talking about a tragedy.”
He said that police needed better vehicles, training and equipment as they grapple with criminal gangs which are “ever more aggressive and militarised”.
It is the second such assault in a week. Last week, a gang of robbers held up an armoured security van on a motorway near Ortona in the central Abruzzo region.
To stop the van, they fired shots, scattered nails on the ground and set off smoke bombs. They then used an explosive device to blow open the sides of the security van and reportedly made off with around €400,000 ($786,938) in cash.
Sign up to Herald Premium Editor’s Picks, delivered straight to your inbox every Friday. Editor-in-Chief Murray Kirkness picks the week’s best features, interviews and investigations. Sign up for Herald Premium here.