* UNHCR cites alleged force used by Italian authorities
* Says many of those sent to Libya need protection
* Italy rejects accsations as false, demands apology
(Adds Italian reaction)
GENEVA, July 14 (Reuters) - The United Nations' refugee agency accused Italy on Tuesday of mistreating African migrants who were stopped from crossing the sea to Europe and diverted to Libya.
Italy rejected the accusations as false and demanded an apology.
UNHCR officials who interviewed 82 migrants intercepted on the high seas on July 1 and sent to detention camps in Libya found that a "significant number from this group are in need of international protection".
Under Italian measures in place since May, at least 900 would-be migrants trying to reach Italy by sea have been sent to other countries, mainly to Libya, according to the office of the United Nations High Commissioner for Refugees.
The Geneva-based agency has repeatedly voiced concern at Italy's new "push-back" policy which it says can prevent access to asylum procedures and undermines international law.
The Italian navy made no attempt to establish the nationalities of the migrants, most of whom were Eritrean, or their reasons for fleeing their homelands, the UNHCR said.
"During interviews, UNHCR heard disturbing accounts alleging that force was used by Italian personnel during the transfer to the Libyan vessel," spokesman Ron Redmond told reporters, saying six Eritreans reportedly needed medical attention as a result.
Italy's European Affairs Minister Andrea Ronchi said the UNHCR "should be ashamed of itself" and should "apologise to Italy."
Ronchi said he had read a letter the UNHCR had released and was shocked that the agency had not asked Italy for its version of events.
"These accusations are rash, false, demagogic, offensive and repugnant and they offend our armed forces who every day around the world demonstrate their morality, dedication, humanity, competence and sacrifice," he said.
The UNHCR said the Italian navy did not offer any food during the 12-hour trip to return them to Libya and seized some vital documents, he told a news briefing, citing the migrants' accounts.
"In view of the seriousness of these allegations, UNHCR has sent a letter to the Italian government requesting information on the treatment of people returned to Libya and asking that international norms be respected," Redmond said.
Sandro Gozi, lower house whip of the opposition Democratic Party, said the government of Prime Minister Silvio Berlusconi should address parliament on the accusations.
The government, which has cracked down on illegal immigration since coming to power last year, has insisted that Italy is not breaking international law with its deportation policy. (Additional reporting by Philip Pullella in Rome)
(Reporting by Stephanie Nebehay; Editing by Richard Balmforth)