Italian police seized an air-to-air missile, machine guns and rocket launchers during raids sparked by an investigation into far-right extremist groups on Monday, a huge haul of weapons that authorities said was almost without precedent.

Police arrested three people, including Fabio del Bergiolo, 50, a former candidate for the neo-fascist Forza Nuova party, whose home was found to contain a huge stash of arms as well as neo-Nazi propaganda and Hitler memorabilia.

"During the operation, an air-to-air missile in perfect working order and used by the Qatari army was seized," police said of the 245-kilogram Matra missile. 

They also found automatic assault rifles that they described as "latest generation" among the cache.

"This is a significant seizure, with few precedents in Italy," said Turin police commissioner Giuseppe de Matteis.

The missile, 3.54 meters long, was made in France and Del Bergiolo had been hoping to sell it for 470,000 euros ($529,000), according to Italian media reports.

The missile was "without explosive charge, but re-armable by people specialized in the field," police said.

"For now, nothing leads us to suspect" an active plot to use the weapons, said counter-terrorism official Eugenio Spina.

The other arrests were a Swiss, 42, and an Italian, 51, accused of holding and marketing the missile, which was found by police at a warehouse near the small Rivanazzano Terme airport in the Pavia Province.

The Mantra Super 530 F was a modernization of the R530 missile that went into service in 1980, and has a range of 25 kilometers, with an explosive charge of 30 kilos.

"It is extremely dangerous and risky to turn it into a missile to fire from the ground, unless you have good engineers and equipment," a missile expert who asked not to be named told AFP.

Similarly, because of its age, it is "extremely unlikely that it can be used, but its use can be changed," he added.

The raids were the result of a police probe into Italian extremists.