Four UN human rights experts have called on Iran to ensure “a fair and transparent final hearing” for three Iranian Christians who are due to appear before the Revolutionary Court in Tehran this weekend.

Pastor Victor Bet Tamraz, Amin Afshar Naderi, and Hadi Asgari were sentenced to between 10 and 15 years in prison last year for a number of charges including “conducting evangelism" and "illegal house church activities," the independent experts said in a February 2 statement.

The men are due to appear on February 4 before Iran's Revolutionary Court, which has the power to end the case, confirm the sentences, or refer the case to the Supreme Court.

The UN expert on the human rights situation in Iran, alongside the experts on freedom of religion, on minority issues, and on the right to health said the charges and sentences were "completely contrary" to Iran's obligations under international law.

"We are additionally concerned about the lack of health care made available to them while in detention and, in particular, about the current health condition of Mr. Asgari, who remains in prison," they said.

The UN experts said they’re also concerned that the prosecution of the three men was not an isolated case.

"Members of the Christian minority in Iran, particularly those who have converted to the faith, are facing severe discrimination and religious persecution," they said.

The experts called on the Islamic republic to "ensure fair trials for all, including the religious minorities in the country."

"We also urge the government to immediately and unconditionally release all those who have been arrested and detained for exercising their right to freedom of religion or belief," they said.

The U.S. said in its 2017 International Religious Freedom Report that Tehran “regulated Christian religious practices closely to enforce the prohibition on proselytizing.”

With reporting by AFP