Iran arrested 17 suspects and sentenced some to death after dismantling a CIA spy ring, an official said Monday, as tensions soar between the Islamic republic and arch-enemy the United States. US President Donald Trump dismissed the report as "totally false". Security agencies "successfully dismantled a (CIA) spy network," the head of counter-intelligence at the Iranian intelligence ministry, whose identity was not revealed, told reporters in Tehran. "Those who deliberately betrayed the country were handed to the judiciary... some were sentenced to death and some to long-term imprisonment." The suspects were arrested between March 2018 and March 2019. "The report of Iran capturing CIA spies is totally false. Zero truth," Trump tweeted. Tehran has been at loggerheads with Washington and its allies since May 2018, when Trump unilaterally withdrew the US from a landmark 2015 deal putting curbs on Iran's nuclear programme in exchange for sanctions relief. The US administration reimposed biting sanctions on Iran, which retaliated by increasing its enrichment of uranium beyond limits set in the nuclear accord. Trump called off air strikes against Iran at the last minute in June after the Islamic republic downed a US drone, one of a string of incidents including attacks on tankers in the Gulf. The tensions have escalated since British authorities seized an Iranian oil tanker on July 4 on suspicions it was shipping oil to Syria in breach of EU sanctions. In what was seen by Britain as a tit-for-tat move, Iran's Revolutionary Guards seized a British-flagged tanker in the strategic Strait of Hormuz on Friday, angering the US ally. - 'The Mole Hunt' - Iran said last month it dismantled a network linked to the US Central Intelligence Agency, state news agency IRNA said at the time, saying it was conducted in cooperation with "foreign allies". On Monday, the counter-intelligence chief said 17 people suspected of espionage had been identified, all of them Iranians. The suspects had been "employed at sensitive and crucial centres and also the private sector related to them, working as contractors or consultants," said the official. The intelligence ministry released a CD with images of what it said were CIA operatives abroad as well as business cards of US diplomats in Austria, Finland, India, Turkey and Zimbabwe allegedly involved in the network. The announcement came as state television started broadcasting a "documentary" titled "The Mole Hunt", a trailer of which was on the disc. It shows re-enactments of spy meetings with an action movie edit plus interviews with officials like intelligence minister Mahmoud Alavi. Some of the spies had been recruited by falling into a "visa trap" set by the CIA for Iranians seeking to travel to the United States. "Some were approached when they were applying for a visa, while others had visas from before and were pressured by the CIA in order to renew them." Others were "lured" by promises of cash, high-paying jobs and even medical services for seriously ill family members. Their mission was to collect classified information and carry out "technical and intelligence operations at important and sensitive centres using advanced equipment," he said. - 'Major defeat' - The top security official alleged the CIA used special stone-like containers to send communications tools and identity documents to its network. "The forgery was clumsy, showing that it was done by the CIA itself," he said, adding that this "proves" it was government-sanctioned. "After they were discovered, CIA officers ordered the spies to destroy all the documents," he added. The official said the CIA had informed the suspects to go to "emergency exits" in cities near the border in case they felt they were in danger. "Of course, they instead met the intelligence ministry's agents and were arrested." He hailed the operation as a "second major defeat of the CIA" following a similar one five years earlier. "They will naturally try to restore and rebuild themselves, and of course we are always vigilant." On June 22 Iran announced it had executed a "defence ministry contractor" convicted of spying for the CIA. Concern over foreign interference is nearly as old as the Islamic republic. The US embassy in Tehran was stormed by students in November 1979 and called the "spy nest". State television recently aired a 30-episode series called "Gando" (an Iranian crocodile species) dramatising with Hollywood flair the Iranian counter-espionage operations. Its first season is inspired in part by the case of Jason Rezaian, the Iranian-American correspondent for the Washington Post in Tehran jailed for 544 days over charges of espionage. Gando portrays him as a spymaster. Rezaian was released in 2016 as part of a prisoner exchange with Washington.