Iranian Foreign Minister Mohammad Javad Zarif gestures as he attends a news conference in Tehran on Oct. 17. (Tima/Reuters)

Iran has arrested another American holding dual citizenship, bringing to four the number of Iranian Americans imprisoned in Tehran after they came under suspicion by hard-line security forces.

Siamak Namazi, a businessman based in Dubai who is in his early 40s, was arrested earlier this month when he was visiting a friend in Tehran, according to a family friend who did not want to be identified. It was not clear whether any charges have been brought against him or what authorities might allege he did.

Namazi, the son of a former governor in the oil-rich Iranian province of Khuzestan, comes from a prominent Iranian family. Namazi’s family came to the United States in 1983 when he was a boy, and he later returned to Iran after graduating from college to serve in the Iranian military. He has consulted on business opportunities in Iran for more than a decade.

A relative of Namazi’s said the family had tried to keep the arrest private, and the relative declined to comment. Word of the arrest of an unnamed Iranian American businessman was first reported by Iran Wire on Oct. 15. Namazi was named as the one who was arrested in several tweets by Iranian Americans earlier this month.

The State Department has repeatedly pressed Iran to release three other imprisoned Americans: Washington Post correspondent Jason Rezaian, who has been held for more than a year, was recently convicted after an espionage trial; former Marine Amir Hekmati of Flint, Mich., who was accused of being a spy when he went to Iran to visit his grandmother, has been held since 2011; and Saeed Abedini, a pastor from Boise, Idaho, was convicted in 2013 of threatening Iran’s national security by participating in home churches. Rezaian, Hekmati and Abedini have all strongly denied the allegations against them.

When asked about Namazi, the State Department declined to confirm his arrest.

“We’re aware of recent reports of the possible arrest in Iran of a person reported to have U.S. citizenship,” said State Department deputy spokesman Mark Toner. “We’re looking into these reports and don’t have anything further to provide at this time.”

Namazi’s arrest suggests that hard-liners in Iran may be trying to create another point of tension with the United States and thereby throw a wrench in the Iran nuclear deal. His arrest came days before an ­agreed-upon date called adoption day, when the Iranian government has committed to begin dismantling some of its nuclear infrastructure.

The part of the government controlled by Iranian President Hassan Rouhani is reformist-minded and seeks more engagement with the West to help jump-start its economy. But hard-liners who control the judiciary and intelligence services oppose the idea, fearful it will open the country to foreign influence. The Revolutionary Guard, Iraq’s most powerful security and military organization, is the entity that would have been responsible for the arrests of the four Iranian Americans.

Iranian Americans such as Namazi are particularly vulnerable to arrest because Iran does not recognize dual nationality.

An Iranian official in Vienna for talks on the Syrian war said the arrest of Namazi and other Iranian Americans should not deter other dual nationals from visiting the country “Iran is safe for Iranian Americans” said the official, who would only discuss the sensitive arrest on condition of anonymity. “Thousands visit Iran regularly. These situations rarely happen, and we hope they can all be resolved.”

Namazi himself has written prolifically about his experiences and conflicted feelings toward the country of his birth. His writings paint the portrait of an idealist who tried to build ­bridges between the country of his birth and the country where he was raised.

He moved to the United States when his father got a job with the United Nations. He earned degrees from the London Business School and from Rutgers and Tufts universities.

Namazi was still young during the Iranian Revolution in 1979, when Ayatollah Ruhollah Khom­eini returned to Tehran after 15 years in exile, and his supporters took over the government.

In journal-like pieces he wrote more than a decade ago for the Iranian, he talked about his decision after graduating from Tufts to return to his birthplace.

“Iran had practically become a dream now, an invented product of childhood imagination,” he wrote. “Still, this land of my dreams was all I thought about. My passion for return was so great, it hurt. The only thing greater than that pain was the fear that I rarely even allowed myself to think of: What happens if I someday return and find out that everything has changed? Then I will be left dry, without a dream, a hope, a home.”

He became a U.S. citizen in 1993. One reason, he later wrote, was to make it easier to get grants and scholarships to pay for his education, and so he could travel without the hassles of an Iranian passport.

A year later, in 1994, he returned to Iran to fulfill his compulsory military duty. He spent 2 1/2 years there, serving as a duty officer in the Ministry of Housing and Urban Planning.

He also wrote often that he thought Iranian Americans could be the bridge between the two cultures that often viewed each other as enemies.

“The new generation must be made to feel that no matter how much time elapses they will be welcomed and treated with respect in the land of their parents,” he wrote in 1998.

“Iran is our motherland, our home, our innocence, our retreat, our passion, our love. It is our unalienable right to travel to and from Iran freely and without restrictions. If you really want us back to help rebuild the country, if you want our children to maintain a bond to the land of their parents, stop treating us like criminals. Why do we have to explain ourselves to you?”

Namazi worked for a time at a family consulting company founded in Tehran and later based in Dubai. According to its Web site, the Atieh Group helped Iranian businesses connect with foreign companies seeking to do business inside Iran. More recently, he worked as the head of strategic planning at the Crescent Petroleum Co. in the United Arab Emirates. It was unclear whether he was employed as a management consultant at the time of his arrest or whether he was working independently.

In recent years, Namazi became outspoken about how financial sanctions had made it difficult to obtain lifesaving medicine in Iran, even though they are technically exempted.

“The West must relax and rationalize the terms of its sanctions regime against Iran to allow more medical goods into the country,” he wrote in an opinion-page piece for the New York Times in 2013. “If it doesn’t, more Iranian men, women and children will suffer needlessly.”

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