Four years on, Iran still seeks missing FBI agent

"All efforts exerted by our country showed no trace of him (Levinson)," foreign ministry spokesman Ramin Mehmanparast told reporters at his weekly news conference broadcast live on state television.

"We will still continue in our effort on a humanitarian basis."

Mystery shrouds the fate of Levinson, who disappeared on Iran's Gulf island of Kish. His wife last heard from him exactly four years ago, on March 8 2007.

Last month, Iran's elite military force, the Revolutionary Guards, denied holding Levinson, as reported on some websites.

On Friday, Clinton urged Tehran for any help in finding him after she declared that he is alive and in southwest Asia.

"Let me say this is an ongoing investigation. I cannot comment any further. What is important is that we work to bring Bob Levinson home safely to his family in Florida," Clinton told reporters.

"And we continue to welcome any help that the Iranian government can provide in determining Mr. Levinson's welfare and whereabouts so that he can be reunited with his family as soon as possible," she said.

Mehmanparast said Clinton's statement indicated that Levinson was not in Iran.

"His family came to Iran and we provided all the information we had to them. Now it is said that he is in southwest Asia which proves he is not in Iran," Mehmanparast said.

Iranian officials have previously denied having any information about the missing American's whereabouts.

Levinson, who retired from the FBI more than a decade ago, had travelled to Kish island reportedly to investigate cigarette counterfeiting in the region.