An American woman reported to have been arrested in Iran for espionage is "safe" and not in Iranian custody, the US state department has said, contradicting Iranian authorities who said she has been detained and has "confessed" to the allegation.

Iranian media, citing police, had reported on Saturday that officials were holding a US woman, identified as 34-year-old Hal Tayalan, on suspicion of spying for the US.

But Mark Toner, a state department spokesman, said on Saturday that the "individual is safe", adding that she is not in Iran at all.

Another US official, who declined to be identified due to privacy concerns, said the woman is in Istanbul, Turkey, and that American consular officials have been in contact with her.

There had been a string of conflicting reports about the case: early on Saturday, a senior Iranian police official reiterated that border guards had detained the woman

Confession claims

Brigadier General Ahmad Geravand, the deputy border police chief, told state radio that authorities arrested the woman on Wednesday while she was filming border crossings and guard posts in Jolfa.

The town is located near the border with Azerbaijan's autonomous region of Naxcivan, close to Armenia.

"During preliminary questioning she confessed to this issue," Garavand told Iranian media on Sunday when asked if the woman was involved in spying.

She was arrested "while she was filming under cover as a tourist, and she was on a mission from the US spy agency," he said in an earlier statement on Saturday.

He added that she was using "advanced filming equipment" to film the "border markets, Jolfa [police] station and the frontier", having been "tasked by Americans".

Geravand also said the woman at one point claimed to be a Swiss citizen.

The Iranian Fars news agency gave the woman's name as Hal Talayan, but the Mehr and ISNA agencies have named her Hal Fayalan, 34.

Iran's Arabic-language al-Alam television station cited a security source as saying that an American woman had been refused entry at a border crossing with Armenia over a visa issue.

Iran is holding two Americans in detention for spying allegations and illegally crossing into the country from northern Iraq.

Shane Bower and Josh Fattal were arrested in July 2009 with Sarah Shourd, who was released last September.

They deny that they were spying and the US has cast doubt that they crossed into Iran at all.