The three envoys said in a statement on Wednesday: "Iran must stop [the] executions of Ahwazi Arabs sentenced to death following a secret, grossly unfair trial."
Philip Alston, UN special rapporteur on extrajudicial, summary or arbitrary executions; Leandro Despouy, special rapporteur on the independence of judges and lawyers; and Manfred Nowak, special rapporteur on torture, said they had written to the Iranian authorities but received no reply.
They said the condemned men, part of a larger group arrested in June 2006 accused of receiving training from US, British and Israeli officials in Iraq, had had no access to lawyers before their trial in the western province of Khuzestan.
Their lawyers, "intimidated" by the threat that charges of "threatening national security" could be brought against them, received details of the prosecution case, reported to be based on confessions extracted under torture, only hours before the trial began.
Nowak said in the statement: "The only element of the cases of these men not shrouded in secrecy was the broadcast on public television of their so-called confessions."
The envoys said they understood that the seven were accused of serious crimes. "However, this cannot justify their conviction and execution after trials that made a mockery of due process requirements," the envoys said.