Foreigners in detention in Japan have suffered serious human rights violations, been denied adequate medical care and legal representation and are kept in solitary confinement for minor breaches of prison rules, Amnesty International said Monday.

In a 46-page report titled "Japan: Ill-treatment of Foreigners in Detention," the international human rights group alleges that Japanese immigration officials, prison guards and police have abused foreigners in detention with violent punishment, sexual assault and racist behavior.

"Foreigners have been beaten by police, denied access to interpreters and lawyers, been forced to sign statements in languages they did not understand and punished for attempting to seek judicial redress for alleged human rights violations," the news release said.

The group submitted its report to the Japanese government for comment, said Pierre Robert, a researcher for the Amnesty International secretariat, at a news conference in Yurakucho, Tokyo. The government has released point-by-point counter-arguments in its response, in which it expressed displeasure at not being given ample time to prepare the reply.

The government also said the group's description of rights to legal representation is "extremely unfair."

"These descriptions are based only on the arguments of those concerned and are written in a conclusive way as if they are objective facts," the government statement said.

Robert said that because the government released its feedback to the group's report, this indicates it is taking the matter seriously. An international team of Amnesty officials, including Robert, visited Japan for three weeks from late May to compile the report, the group officials said.