The State Department issued a worldwide warning for American citizens overseas following President Donald Trump's announcement on Jerusalem.
Palestinian Authority President Mahmoud Abbas said he warned Trump of the "dangerous consequences" of such a move on security, the peace process, and stability in the region.
The US decision to recognize Jerusalem as Israel's capital may become a "legitimate reason" to attack American troops in Iraq, Shia paramilitary group Harakat Hezbollah al Nujaba said.
Dozens of Iraqis protested the decision in Baghdad, carrying signs saying "Jerusalem is Arab" and vowing to return in greater numbers the following day after Friday prayers.
An Iran-backed militia operating in Iraq echoed Baghdad's statement, saying Trump's "stupid decision" would be a "legitimate reason" to attack US troops in Iraq, Reuters reported.
Not only Iraq is protesting this decision of trump.
It fights under the umbrella of the Popular Mobilisation Forces (PMF), a mostly Iranian-backed coalition of Shi'ite militias that played a role in combating Islamic State.
Turkey, a US and North Atlantic Treaty Organisation ally, threatened to sever ties with Israel if the USA were to make such a declaration and the Palestinians said they would cut off contact with their US government liaisons, CBS News reported.
Meanwhile, the Palestinian group Hamas - recognized as terrorists by the USA - threatened its own retaliation against Israel following Trump's declaration of the new US policy, a separate Reuters report said. Hamas, the Palestinian Islamist group that both Israel and the United States consider a terrorist group, has called for a third intifada, or uprising, against Israel.
"We have given instruction to all Hamas members and to all its wings to be fully ready for any new instructions or orders that may be given to confront this strategic danger that threatens Jerusalem and threatens Palestine", Haniyeh added.
Just as President Donald Trump issued his controversial declaration of Jerusalem as Israel's capital, the State Department told its citizens around the world to exercise vigilance in response to concerns about terrorism and civil unrest.