The lawyer for an Iranian American jailed in Iran urged Tehran to allow him to leave jail temporarily if his elderly father undergoes surgery in the country.

His son, Siamak Namazi, 49, remains in prison. Both son and father have been accused of security offences and convicted in an unfair trial. The US government has described the charges against both as baseless.

"Siamak Namazi has served six years of his 10-year prison term without a single day of furlough ... From a human and emotional point of view, in these difficult conditions (he) wants to be with his elderly father, who has no other children in Iran," attorney Hojjat Kermani told the Emtedad website.

US-based lawyers urged Tehran last week to let him leave the country for medical care, saying he needed immediate surgery for an arterial blockage.

Kermani urged Iranian authorities to allow Baquer Namazi to leave Iran for medical treatment or at least temporarily release his son if he is to undergo surgery in Iran. This was required by "the law and the principles of Islamic and humanitarian compassion", Kermani told Emtedad.

Iranian Americans, whose US citizenship is not recognized by Tehran, are often jailed in what human rights organizations say is in effect hostage taking.

With Reporting by Reuters