TEHRAN, Iran — Iranian officials announced Monday that 17 people who were allegedly spies working for the CIA have been captured.

The Iranian Intelligence Ministry held a briefing Monday at which they said the alleged spies are Iranian citizens but trained by the CIA.

Some of those arrested have been sentenced to death, while others will be handed long jail sentences, the Intelligence Ministry said.

It was not immediately clear when they were arrested.

The Iranian government occasionally makes similar claims and it was not immediately possible to determine whether they are legitimate. The U.S. government never acknowledges CIA recruitment abroad but President Donald Trump blasted the reported arrests on Twitter as "totally false."

At Monday's briefing held by Iran's head of counterespionage, an official claimed the 17 accused were lured into spying while applying for or renewing U.S. visas or while attending conferences abroad with promises of money and opportunities to work in the United States.

The accused were given surveillance equipment by handlers to place in sensitive government locations and received "extensive training" by the CIA in order to communicate from Iran without being detected, officials claimed. They were also given fake identification.

Some of those captured agreed to cooperate with Iranian authorities and are now helping to work against the U.S., officials said.

The ministry distributed files to reporters attending the briefing that they say identifies the alleged officers. NBC News has obtained a copy of the files that they say include audio exchanges between alleged CIA operatives and their Iranian sources, business cards and photos of alleged CIA officers and their families, and a copy of an Iranian documentary that claims to uncover the identities of the alleged spies.

The announcement comes amid renewed hostility between Iran and the West.

On Friday, Iran's Revolutionary Guard seized a British oil tanker in the Strait of Hormuz.

Senior U.S. defense officials said that U.S. Marines jammed an Iranian drone in the Strait of Hormuz on Thursday, bringing it down and destroying it.

A U.S. surveillance drone was also shot down last month by Iran's Revolutionary Guard. In the aftermath of the incident, Trump confirmed that he was "cocked and loaded" to strike Iranian targets but decided to call the strikes off, saying the loss of life would make it a disproportionate response.

Arouzi reported from Tehran, Givetash reported from London.