The United States on Thursday imposed sanctions on Russia’s domestic security service FSB and the intelligence unit of Iran’s Islamic Revolutionary Guard Corps (IRGC) accusing them of being responsible or complicit in the wrongful detention of Americans overseas, senior administration officials said.

The sanctions also targeted four senior commanders within IRGC’s IO, although among them were at least one individual who had been already been subject to previous US sanctions. FSB was also subject to previous US sanctions.

Speaking to reporters in a briefing call on the condition of anonymity, senior Biden administration officials said Thursday’s move aimed to show that there would be consequences for those who tried to use US citizens for political leverage or seek concessions from Washington.

“Our action is a warning to those around the world who would wrongfully detain US nationals of the potential consequences of their actions,” a senior administration official briefing reporters on the condition of anonymity said.

“Today’s sanctions are one of a series of efforts - some public like this, some private - to secure the release of US Nationals wrongfully held overseas, to promote accountability for the culprits, and by doing so, to prevent and deter the next set of cases from arising in the first place.”

The official added that Thursday’s measures were the first set and that there were more sanctions being worked on.

Russia and Iran, two US adversaries, hold a number of American citizens in their prisons, detentions Washington says are wrongful and politically charged.

Last month, Russia’s FSB arrested Evan Gershkovich, a US reporter working for the Wall Street Journal and accused him of espionage, a charge he has denied. Paul Whelan, a former US marine, has also been serving a 16-year jail sentence in a Russian penal colony over spying accusations. He denies any wrongdoing.

Ties between the United States and Russia have sunk to their worst in decades following Moscow’s invasion of Ukraine, however the two former Cold War foes have managed to carry out compartmentalized diplomacy which resulted in two prisoner swaps last year.

In one, Washington has secured the release of US basketball star Brittney Griner who was held in Russia on drug charges, by commuting the sentence of Russian arms dealer Viktor Bout.

The plight of Americans detained by foreign governments has moved into the spotlight with Griner’s case. Although the US government does not provide figures, there are more than 60 such detainees, according to the James Foley Foundation, named after an American journalist abducted and killed in Syria.

At least several of them are jailed in Iran.