TEHRAN -The case of three US hikers held in Tehran is not linked to that of an Iranian nuclear scientist who returned from the United States, an Iranian official said Saturday on the one-year anniversary of their detention.

"American officials and the Western media are trying to link the two cases of Shahram Amiri and the three US spies... while these two are not related to each other," Kazem Jalali, spokesman of parliament's foreign policy committee, was quoted as saying by the official IRNA news agency.

"The case of the three American spies is being processed in the judicial system," Jalali said.

The lawmaker insisted the three American hikers had entered Iran "illegally," adding they would be judged based on the Islamic republic's law against espionage.

He was comparing the case of the hikers with Iranian nuclear scientist Shahram Amiri, who claimed he was abducted by US spies last year before returning home in July.

The comments came after US President Barack Obama called on Iran to "immediately release" the trio, saying they had never worked for the US government and committed "absolutely no crime."

The hikers -- Shane Bauer, 27, Sarah Shourd, 31, and Josh Fattal, 27 -- have "never had any quarrel with the government of Iran, and have great respect for the Iranian people," the US president said.

Obama's appeal came on the one year anniversary of the hikers' arrest in the Islamic republic.

US Secretary of State Hillary Clinton said on July 13 that Amiri was "free to go" home from the United States after he took refuge in the Iran section of Pakistan's US embassy in Washington, unlike the three hikers.

"He is free to go, he was free to come," Clinton said, refuting Iranian allegations that Amiri was being held in the United States at the time against his will.