Britain's Foreign Office said on July 6 that reports of the arrest of a British diplomat in Iran "are completely false."
Iranian media reported earlier that the Islamic Revolutionary Guards Corps (IRGC) detained several foreign nationals, including Britain's second-ranking diplomat, over accusations of spying.
The IRGC identified and arrested the foreigners, saying they were observed by drones taking soil samples in a prohibited area in the central desert of Iran, the IRGC-affiliated Fars news agency said.
The country's state-run IRNA news agency reported that the foreigners had been arrested but did not say when or whether they were currently in custody.
Britain's deputy ambassador is among the people who went to the Shahdad desert with his family as a tourist, Fars reported.
A photo accompanying the Fars report showed four people in a desert setting. Another photo showed two people who appear to be looking for soil samples after parking their bicycles.
"These spies were taking earth samples in Iran's central desert where the Revolutionary Guards' aerospace missile exercises were conducted," state TV said.
Fars claimed the British diplomat, Giles Whitaker, was expelled from the country after apologizing.
A spokesperson for Britain's Foreign Office said: "Reports of the arrest of a British diplomat in Iran are completely false."
State TV also identified Maciej Walczak, a Polish scientist at Kopernik University in Poland, as one of the accused foreigners. The report said another of the detained individuals is the husband of Austria's cultural attache in Iran.
It said their sample collection coincided with a missile test in Iran's southern Kerman Province.
The United States earlier on July 6 designated 15 individuals and entities for alleged engagement in illegally selling and shipping Iranian oil and oil products.
The U.S. State Department said in a statement that the entities -- located in Iran, Vietnam, Singapore, the United Arab Emirates, and Hong Kong -- "have supported Iranian energy trade generating millions of dollars' worth of illicit revenue."
The U.S. Treasury Department said the entities and individuals used a web of Persian Gulf-based front companies to facilitate the delivery and sale of the Iranian oil and oil products from Iranian companies to East Asia.
"While the United States is committed to achieving an agreement with Iran that seeks a mutual return to compliance with the Joint Comprehensive Plan of Action, we will continue to use all our authorities to enforce sanctions on the sale of Iranian petroleum and petrochemicals," Brian Nelson, undersecretary of the treasury for terrorism and financial intelligence, said.
Talks to revive the Iran nuclear deal have been stalled for months. Iran has said it is ready for new indirect talks to overcome the last hurdles to revive the 2015 nuclear deal amid a growing crisis over the country’s nuclear program.