Tehran  - An Iranian-American radio reporter has been detained in Tehran on charges of illegal press work, media reports said Monday.

According to her Iranian-born father, the 31-year-old Roxana Saberi, a US citizen, has been detained in an undisclosed location since a month ago.

Iran's daily Etemad was the first local newspaper to report her arrest.

Without confirming Saberi's detention, Foreign Ministry spokesman Hassan Ghashghavi said Monday that Saberi, who works for US-based National Public Radio, had been denied official press accreditation since 2006 and therefore would have been working illegally.

Foreign correspondents and Iranian nationals working for foreign press are obliged to obtain official accreditation from the Ministry of Culture and Islamic Guidance, without which any press activity is forbidden.

US State Department deputy spokesman Gordon Duguid told reporters in Washington that the United States has issued a request through the Swiss about Sebari's status. The United States and Iran do not have formal diplomatic relations.

"The State Department has been in touch with her family, and we're working with them, offering them what assistance that we can," he said. "At the moment, we don't have details back yet from our request through the Swiss."

Saberi's father told US media that his daughter was arrested after she purchased a bottle of wine - the consumption of which is officially illegal in Iran - but he considered this just a pretext.

In the first half of the decade, the Culture Ministry allowed the expansion of the presence of foreign reporters and news bureaus but gradually introduced stricter rules for the accreditation process. dpa