* Italian police arrest three Italians, three Albanians
* Accused of kidnapping Berlusconi accountant; extortion
* Mystery surrounds nature of documents they tried to sell
ROME, Nov 19 (Reuters) - Italian police on Monday disclosed an attempt to extort former Prime Minister Silvio Berlusconi by bandits who held his accountant hostage and offered to sell sensitive documents for 35 million euros ($44.47 million).
Police told a news conference in Milan they had arrested three Italians and three Albanians on suspicion of kidnapping and extortion but many questions remained unanswered in what the Italian media said remained a mysterious episode.
Police said three men held Giuseppe Spinelli and his wife hostage at their home overnight on Oct. 15 and demanded money in exchange for documents they said could help Berlusconi win an appeals trial.
It was not clear from what emerged at the news conference what type of documents the extortionists had. Spinelli told police he saw some of the documents but police did elaborate.
The aggressors told Spinelli the papers could overturn a 2011 court ruling that forced Berlusconi's Fininvest empire to pay 560 million euros to rival media company CIR in compensation for a takeover battle over publisher Mondadori that was marred by corruption.
The extortionists forced Spinelli to call Berlusconi on the morning of Oct. 16 and tell him about the documents.
Berlusconi called his lawyer, who in turn called Spinelli while the bandits were still there. They left after an agreement to get back in touch with Spinelli and at least one other telephone contact was made.
The authorities were not informed until more than 24 hours later, when Berlusconi's lawyers filed a complaint.
Niccolo Ghedini, Berlusconi's lawyer, told reporters he called Spinelli and told him to ask the bandits to bring the documents to Berlusconi's residence in Milan.
"Spinelli told me he could not and I could tell from the tone of his voice that something was wrong. Spinelli was under shock. He was worried about his wife and his daughter and his granddaughter, who all live in the same neighbourhood," Ghedini said.
Police told the news conference no money was handed over and had no explanation why the complaint was not made for 24 hours.
In an investigation that was kept secret for more than a month, police used closed circuit television footage to track down the extortionists, including three accomplices who did not take part directly in the kidnapping.
Spinelli, an accountant in charge of Berlusconi's finances, paid showgirls to attend the media mogul's infamous "bunga bunga" parties, according to testimony he gave an Italian court. ($1 = 0.7871 euros) (Writing by Philip Pullella; Editing by Robin Pomeroy)