Iran says it is holding a U.S. Navy veteran, confirming media reports about a case that risks further escalating tensions with Washington.

The New York Times reported on January 7 that Michael White, 46, was arrested while visiting Iran and had been held since July on unspecified charges.

On January 9, Iranian state news agency IRNA carried a statement by Foreign Ministry spokesman Bahram Qasemi that confirmed the arrest, but did not specify when it had happened or what crime he was accused of.

Qasemi was quoted as saying that Iran had informed the U.S. government about White's arrest within days of when he was taken into custody in the city of Mashhad "some time ago."

The spokesman added that White's case was going through the legal process and officials will make a statement at the appropriate time.

The U.S. State Department said it was "aware of reports" of the detention but did not provide further details, citing privacy considerations.

The New York Times has quoted White's mother, Joanne, as saying she learned three weeks ago that her son was being held at an Iranian prison.

She said her son had visited Iran "five or six times" to see an Iranian woman she described as his girlfriend.

White's incarceration was also reported on January 7 by Iran Wire, an online news service run by Iranian expatriates.

White's imprisonment could further worsen relations between Washington and Tehran, longtime foes.

Tensions have been high since U.S. President Donald Trump pulled Washington out of a landmark nuclear deal with Iran and reimposed crippling economic sanctions against Tehran last year.

At least five Americans have been sentenced to prison in Iran on espionage-related charges.

Among them is Xiyue Wang, a Princeton University student, who was given a 10-year sentence for espionage. He was arrested in August 2016 while conducting research for his dissertation on Iran's Qajar dynasty. Both Wang and the university deny the claims.

Baquer Namazi, a retired UNICEF official, and his son Siamak, an Iranian-American businessman, were sentenced in 2016 to 10 years in prison for spying and cooperating with the U.S. government. The charges were denied by the family and dismissed by U.S. authorities.

Bob Levinson, a former Federal Bureau of Investigation agent, vanished on Iran's Kish Island in 2007 while on an intelligence mission. Tehran has said it has no information about his fate.

With reporting by AP, AFP, dpa, The New York Times