LONDON - Two rights groups urged the Iranian judiciary on Thursday to quash death sentences against five members of Iran's Arab minority and halt their executions on grounds of torture and unfair legal proceedings.London-based Amnesty International and Human Rights Watch, which is based in New York, said in a statement the five had been sentenced last year on terrorism-related charges because of their links to a banned cultural institute that promoted their Arab heritage.Arab minorities in Iran are mostly based in the southwest. They complain of economic deprivation and systematic discrimination by authorities which, they say, try to dilute their Arab identity.There are no official figures for the size of the Arab population but independent estimates count Arabs as the majority in oil-rich Khuzestan province, which borders Iraq.Iranian officials maintain they have no problems in Khuzestan and dismiss talk of human rights violations against Arab Iranians in Ahvaz as propaganda.No officials were immediately available to comment on the statement by the two rights groups.Four members of Iran's Arab minority were executed last year. United Nations human rights experts said they were sentenced to death after an opaque trial whose fairness was questionable.Their death sentences were upheld last week and they were transferred from Karoun prison in Ahvaz, capital of the southwestern province of Khuzestan. Their families no longer know where they are being held, the statement added."The reported transfer of these men to an unknown place is an extremely worrying development," said Ann Harrison of Amnesty International. "We fear the authorities may be planning to execute them imminently."Families of the five men, two of whom are brothers, say they were subjected to "physical and psychological torture" during their detention, the statement said.It added that security forces had arrested all five at their homes in early 2011 in advance of the sixth anniversary of protests by ethnic Arabs in April 2005.On Wednesday, 30 human rights organizations and campaigners, including Iran's Nobel Peace Prize winner Shirin Ebadi and Ahwazi Arab campaign groups, urged Iran to stop the implementation of the death sentences against the five men."Among ethnic minorities in Iran, Ahwazi Arabs are subjected to some of the most severe repression from the central government," read their joint statement.