The conflict between Iran and the United States moved Monday to the field of espionage.
The Iranian government said it arrested 17 spies suspected of working for the CIA, the US intelligence agency, and said it sentenced some of them to death.
The Iranian Ministry of Intelligence reported that the alleged spies collected nuclear, military and other sector information.
The president of the United States, Donald Trump, dismissed the information and said it is "totally false."
"The information that Iran captured CIA spies is totally false. Zero truth. Just more lies and propaganda (like its downed drone) of a religious regime that is failing and has no idea what to do. Its economy is dead and will worsen much more. Iran is a total disaster! "Trump wrote on Twitter.
The tension between Washington and Tehran has worsened recently.
Trump withdrew the United States last year from the nuclear deal that Iran and six world powers reached in 2015, and the U.S. reinstated severe economic sanctions on Iran.
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In recent weeks the two countries have been close to unleashing a military conflict in the Gulf.
In statements made shortly after the Iranian announcement about the arrests, Trump said: "It is getting harder for me to want to reach an agreement with Iran."
What is known about the case of spies
The Iranian government says that the spies who allegedly worked for the CIA were arrested within a 12-month framework that ended last March.
A senior intelligence official told reporters that the 17 people are Iranians who work in "sensitive centers" of military, nuclear and private sector facilities, and that they acted independently of each other.
The official did not say how many were sentenced to death or when the sentences were issued.
"Sentences for these spies have been issued. Some of them will be executed as 'corrupters on earth' [a charge that is punishable by death under Islamic law in Iran]," said the head of the Espionage Department of the Ministry of Intelligence, as cited by the Iranian Student News Agency.
On Sunday, Iranian Intelligence Minister Mahmud Alavi announced the next broadcast on Iranian television of a documentary about the arrests of "US-linked spies."
The Intelligence Ministry released a CD with a documentary trailer, spy meeting reconstructions and interviews with authorities, including Alavi himself.
Alavi explained that some of the spies fell into a "CIA-mounted trap" for Iranians who want to travel to the United States.
The minister added: "Some were approached [by the CIA] when they were applying for a visa, while others already had a visa and were pressured by the CIA to want to renew it."
Others were tempted with offers of money, high-paying jobs and medical services, he continued.
Last month, Iran said it dismantled a network linked to the CIA, but it is not clear if Monday's announcement is related to the same case.
A power struggle in Iran?
Analysis of Kasra Naji, BBC Persian service
Many observers of Iranian politics welcome this latest Iranian claim with deep skepticism.
While the Iranian Ministry of Intelligence says that last month it dismantled a spy band connected to the CIA, confusingly, adding that 17 alleged spies were already arrested last year.
Some believe that 17 is the sum of all those arrested on suspicion of espionage over several years. They are all Iranians.
According to a report by Evin's famous Iranian prison, there are many prisoners accused of spying for several countries.
But the reason why the Ministry of Intelligence now appears with this story probably has more to do with its rivalry with the intelligence unit of the Revolutionary Guard than with new arrests.
Only two weeks ago, Iranian state television aired the last episode of a docudrama that glorifies the intelligence unit and portrays the government of President Hassan Rohani as ineffective and weak in the face of Western espionage.
Now, the Ministry of Intelligence strikes back with its own documentary in which it claims its greatest success against espionage.
It seems that rival intelligence agencies in Iran are involved in a very public power struggle that everyone can watch on state television.
Chronology of the current crisis
Tension between Iran and the United States and the United Kingdom remains high after a series of incidents in a key area for world navigation: the Strait of Hormuz.
On Friday, July 19, Iran captured a British flag tanker in the waters of the Strait of Hormuz. Tehran had already announced that it would take action in response to the capture by the United Kingdom of an Iranian oil tanker off the coast of Gibraltar in early July.
Trump announces that the US navy shot down an Iranian drone, but Iran denies it.
Last month, Iran shot down a US surveillance drone over the strait and alleged that it violated Iranian airspace. But the US military responded that the drone was flying over international waters at that time and condemned the incident as an unprovoked attack.
The United States also held Iran responsible for two separate attacks on oil tankers in the Gulf of Oman in May and June, accusations Tehran denies.
This escalation of tension dates back to the US abandonment. of the nuclear agreement in May 2018 and the consequent reimposition of sanctions on Iran.