The president’s remarks followed the US assassination of Qasem Soleimani, a top Iranian general, during a drone strike.
Soleimani’s killing was a serious escalation between the 2 nations, and Iran vowed to require “severe revenge”.
Writing on Twitter, Mr Trump accused Iran of “talking very boldly about targeting certain USA assets”.
He said the US had identified 52 Iranian sites, some “at a really high level & important to Iran & the Iranian culture”, and warned they might be “HIT in no time AND HARD” if Tehran struck at the US.
The president said the targets represented 52 Americans who were held hostage in Iran for quite a year from late 1979 after they were taken from the US embassy in Tehran.
Shortly after the president’s tweets were posted, the web site of a United States government agency seemed to are hacked by a gaggle calling itself “Iran Cyber Security Group Hackers”. A message on the American Federal library Programme site read: “This may be a message from the Islamic Republic of Iran.
“We won’t stop supporting our friends within the region: the oppressed people of Palestine, the oppressed people of Yemen, the people and therefore the Syrian government, the people and government of Iraq, the oppressed people of Bahrain, truth Mujahideen resistance in Lebanon and Palestine, [they] will always be supported by us.”
The web page contained a doctored image of President Trump, depicting him being hit within the face and bleeding at the mouth. “This is merely small a part of Iran’s cyber ability!” read text on the location .