(CNN) -- Two videos surfaced Wednesday of a man claiming to be missing Iranian nuclear scientist Shahram Amiri, in which he says he has escaped from U.S. agents and is in hiding in Virginia.
This is the third time that videos allegedly showing Amiri have been circulated on the internet.
In one, he said he had been kidnapped by U.S. agents. Another contradicted that claim and said he was living freely and studying in Arizona.
In one of the videos posted on YouTube Wednesday and dated June 14, the man again says that he was brought against his will to the United States and fears he will be discovered and re-arrested.
"I am Shahram Amiri, the son of the Islamic Republic of Iran, who with God's help succeeded in running away from the U.S. security agents in the state of Virginia. I am [temporarily] at a safe place and I am trying to do this video but it is quite possible that I may shortly be again arrested by American security agents."
He goes on to say: "I am not free here and not allowed to contact my family or other people. If I face any problems or if I do not return to my country soon, the government of the U.S. would be directly responsible for it."
Amiri, a researcher at Tehran's Malek Ashtar University, mysteriously disappeared last June while on a religious pilgrimage to Saudi Arabia, according to Iran's state-run Press TV.
Iran accused the United States of involvement in Amiri's disappearance. The U.S. State Department denied that charge but has been tight-lipped on whether Amiri defected.
CNN could not independently verify the authenticity of the videos, nor the identity of the man in them.
As policy, the CIA does not comment on defections. But a U.S. official, who is not authorized to talk to the media about such issues, told CNN it would be "ludicrous, absurd and even preposterous" to claim an individual was kidnapped by the United States and held against his will.
"If he is who people think he is, the U.S. would be in contact with the person," the official said.
And if he were being held against his will, "how would he have been able to produce any of the videos?" the official said.
In the second video that surfaced Wednesday and was dated June 23, the man claiming to be Amiri reassures his family about his well-being.
"I want to let my beloved family know that I am OK and they should not worry about my health," he says. "With God's help I shall return to my beloved country in the next few days. I want them to be, as always, strong and patient and to pray for my safe return. I hope to see you in our beloved country."
Tehran blamed Washington for Amiri's disappearance shortly after revelations surfaced that Iran has been building a second uranium enrichment facility near the city of Qom. After that, tensions over Iran's nuclear program mounted.
Iran says its nuclear energy is solely for civilian purposes. But the United States pushed the United Nations to punish Tehran for its nuclear ambitions. The Security Council recently slapped a fourth round of tough sanctions on the Islamic republic.
It's unclear how much information Amiri was privy to in Iran.
CNN's Shirzad Bozorgmehr and Pam Benson contributed to this report.