Iran has confirmed the arrest of an American citizen after US media reports about the case.
The New York Times reported on Monday that 46-year-old US Navy veteran Michael White was arrested while visiting Iran and has been held since July on unspecified charges.
Iranian state news agency IRNA carried a statement by foreign ministry spokesman Bahram Qassemi on Wednesday confirming White's arrest.
The statement did not specify when White was arrested or what crime he was accused of.
Qassemi said Iran had informed the US government about White's arrest within days of him being taken into custody and denied that White had been poorly treated.
"These sorts of reports are lies and improper and are seriously rejected," IRNA quoted Qassemi as saying.
White's case is going through the legal process and officials will make a statement at the appropriate time, he added.
The case is likely to further worsen relations with the United States.
President Donald Trump withdrew from an international nuclear agreement with Iran and re-imposed sanctions last year that hit the Iranian economy hard.
Several Americans have been detained in Iran in recent years and Trump warned in 2017 that Tehran would face "new and serious consequences" unless all unjustly held US citizens were freed.
White's mother, Joanne, told the New York Times her son had visited Iran "five or six times" to meet his Iranian girlfriend.
She reported her son's disappearance after he failed to return in July but learned from the State Department only three weeks ago that he was being held in Iran.