Italian auctioneers reopened some decades-old wounds from the country's years of lead on Thursday with the sale of documents from the Red Brigades guerrilla group who shocked the world in 1978 by kidnapping and murdering a former prime minister.

Bolaffi auction house in Milan sold 17 propaganda leaflets and statements issued by the Red Brigades, including the infamous Communication number 6 pronouncing the group's death sentence on former prime minister Aldo Moro, who was murdered in May 1978 after a 55-day kidnapping.

Moro's killing marked the culmination of a campaign of murder and kidnapping aimed at destabilising Italy in what became known as the years of lead.

Lot number 243 was bought by a private library in Milan headed by Marcello dell'Utri, a close ally of ex-prime minister Silvio Berlusconi and known as an avid collector.

According to Bolaffi's Chief Executive Maurizio Piumatti the library is home to the most extensive archive of the years of lead in the 1970s and early 1980s.

Some victims and family members of those killed by the group have accused Bolaffi of trying to make money out of tragic events, arguing the documents should have been donated to public archives and not private collections.

It's an absolute disgrace. They went under the hammer as if they were kids' postage stamps, said Giovanni Berardi, President of the European Association of Terrorism Victims outside the auction house.

Berardi's father Rosario, a former police chief, was killed by the Red Brigades in 1978 in Italy's northern city of Turin.

We tried to bid for the lot but 17,000 euros is more than I make in a year, he said.

Piumatti acknowledged that selling the documents might upset those who had suffered at the hands of the group but insisted they were of historical value.

From our point of view these are historical objects, he said, adding the commissions on the sale from the auction would be given to charity.

Bolaffi said it had received the Red Brigades documents by an unidentified seller who had found them at the beginning of the 1990s amongst rubbish in a house once used by left-wing groups for their meetings.

I can totally rule out that they come from any courtroom material. On one of them it's written 'found in the bathroom', Piumatti said.

Carmine Abbagnale, regional secretary of police trade union COISP who was protesting outside the auction house, said the documents should not be in private hands.

These are unpublished documents and should be handed over to judicial authorities, said Abbagnale, who is a member of a police force which took part in a gunfight with members of the Red Brigades on the streets of Milan in 1977.

Most of the leading members of the Red Brigades had been captured and imprisoned by the mid-1980s.

For many years, members on the run found refuge in France which declined to extradite them claiming convictions against them were of dubious legality.

(Reporting By Stephen Jewkes, editing by Paul Casciato)