Kuala Lumpur - A UN body has determined that former Malaysian opposition leader Anwar Ibrahim has been jailed illegally and called for his immediate release, according to a copy of the opinion released Monday by his family.Anwar, 68, was jailed in February for five years after earlier being convicted for sodomising a former male aide. He denies the charge, calling it a frame-up by Malaysia's long-ruling government to halt recent opposition political gains.The opinion by the UN Working Group on Arbitrary Detention concluded that Anwar's imprisonment was "arbitrary", that he was denied a fair trial, and was jailed for political reasons."The Working Group considers that the adequate remedy would be to release Mr Ibrahim immediately, and ensure that his political rights that were removed based on his arbitrary detention be reinstated," said the opinion, dated September 15.It also said Anwar's treatment in prison violates international prohibitions against "torture or other cruel, inhuman or degrading treatment."No immediate reactionAnwar's family has complained that he is being held in a filthy cell with only a thin foam mattress despite chronic back trouble, and has been denied adequate medical care for a host of ailments include erratic blood pressure and a shoulder ailment."I am deeply grateful that the United Nations has called for Anwar's release," said Nurul Izzah Anwar, the former opposition leader's daughter and a member of parliament."Its strong stance in solidarity with my father sends a clear and unequivocal message to Prime Minister Najib Razak, and ensures that the sharp decline in human rights under his administration will not go unnoticed."No immediate reaction was seen from Najib's government.The UN working group is a five-member body currently comprised of experts from Australia, Benin, Mexico, South Korea, and Ukraine.The case is the second such disputed conviction for Anwar, a former deputy prime minister who was ousted from the ruling party in a late 1990s power struggle and jailed on sodomy and corruption charges widely viewed as politically motivated.After his release in 2004, he helped unite Malaysia's previously divided opposition into a formidable alliance.His latest conviction has been criticised by the United States - which said it raised questions over rule of law - as well as other nations and international human rights groups.