Burning American and Israeli flags, Iranians rallied after Friday prayers against the U.S.'s decision to designate the country's powerful Revolutionary Guards as a foreign terrorist organization.

Thousands of worshippers came out of the mosques chanting traditional anti-U.S. slogans at such rallies of "Death to America" and "Death to Israel." Iranian state media said similar demonstrations took place in other Iranian cities and towns.

The U.S. government this week designated the Revolutionary Guard as a terrorist group to increase pressure on Iran, isolate it further and prompt authorities to divert some of the financial resources Tehran uses to fund militant activity in the Middle East and beyond.

Iran responded by designating all U.S. forces as terrorist and labeling the U.S. a "supporter of terrorism."

Also Friday, Foreign Minister Mohammad Javad Zarif sent a letter to the U.N. Security Council and Secretary-General Antonio Guterres stressing that Iran would hold the U.S. accountable for any future provocations against Iranian Revolutionary Guard Corps, or IRGC.

According to the state-run IRNA news agency, Zarif said the U.S. and "several puppet governments will bear responsibility for dangerous consequences of the adventurism."

"The provocative move will raise tensions to an uncontrollable level and increase threats in the region," he said, adding that the Revolutionary Guard is at the forefront in fighting terrorism and extremism.

The commander of Iranian ground troops, Brig. Gen. Kioomars Heidari, said the U.S. decision was self-destructive as the Americans "have put their own forces, particularly the U.S. Central Command, in danger across the world."