The Trump administration disputed a claim by Iran's state media Monday that authorities in the Middle East country arrested 17 secret agents recruited by the Central Intelligence Agency to spy on its nuclear and military sites.

Iran's semiofficial Fars news agency said some of them have been sentenced to death. It was not clear whether all the alleged spies were Iranian nationals.

There is no U.S. embassy or diplomatic presence in Iran, meaning there is no obvious diplomatic cover for American agents who may operate inside Iran.

The Fars news agency published images that Iran's Intelligence Ministry said show the CIA officers who it claimed were in touch with the suspected spies. The ministry said the agents infiltrated organizations and institutions in Iran's private sector.

There was no immediate reaction from the CIA, which rarely comments on its national security activities. U.S. Secretary of State Mike Pompeo dismissed Iran's announcement. "The Iranian regime has a long history of lying," he said in an interview on Fox News. In a tweet, President Donald Trump called Iran's claim "totally false. Zero truth." He said Iran's economy is "dead" and "will get much worse."

The arrests occurred over the past few months as Iran’s nuclear deal with world powers has been under increasing strain after Washington's withdrawal a year ago and its renewal of economic sanctions on Iran. Tensions between the United States, Britain and Iran have spiked in the Persian Gulf region.

Soon-to-depart British Prime Minister Theresa May chaired an emergency security session Monday to discuss how to respond to Iran’s seizure of a British-flagged tanker in the Strait of Hormuz, a waterway that is vital to the world’s oil supply.

The Stena Impero tanker was seized Friday and is in a heavily guarded Iranian port. Britain is considering a number of options, though not military, to raise the pressure on Iran. The seizure followed a threat by Iran to respond to Britain's impounding of an Iranian oil tanker off Gibraltar, in the Mediterranean Sea, that Britain said was on its way to Syria in breach of European Union sanctions. Iran disputed that its tanker tried to reach Syria, a close ally.

An audio recording released Sunday revealed the tense moments before the Stena Impero was seized by Iranian Revolutionary Guard forces rappelling from helicopters onto the ship's deck. Iran alleged that the tanker collided with a fishing boat, then failed to respond to calls from the smaller boat.

Washington said it wants to lead efforts to coordinate safety for vessels passing through the Persian Gulf. In the Fox News segment, Pompeo said, "It falls to the United Kingdom to take care of their ships."

British Foreign Secretary Jeremy Hunt said a European-led maritime protection mission would ensure safe passage of commercial ships in the region.

Hunt called the Stena Impero's seizure an "act of piracy."

Unlike the United States, Britain is still signed up to the nuclear deal with Iran. Speaking in Parliament, Hunt said his country was not interested in joining Trump's "maximum pressure" campaign against Iran that includes onerous sanctions, asset freezes and the designation of Iran's Revolutionary Guard – an organization with broad-based links to Iran's military and businesses – as a terrorist organization.

State TV in Iran aired a documentary Monday that purports to show a CIA officer recruiting an Iranian man in the United Arab Emirates. It was not clear whether the broadcast was connected to the announcement about the alleged spies.

Last month, Iran's Intelligence Ministry claimed it "penetrated the U.S. safe system in cyberspace" used by the CIA for communicating with American agents, according to Press TV, a state-run network that broadcasts in English.

"We're ready for the absolute worst," Trump said at the White House on Monday in response to a question about whether his administration is closer to negotiating or war with Iran. "(They) disrespected the United States. They shouldn’t have done that. ... Frankly, it’s getting harder for me to make a deal with Iran."