On Friday, a U.S. drone attack ordered by President Donald Trump killed Qassem Soleimani, commander of the Quds Force of Iran's Islamic Revolution Guards Corps, and Abu Mahdi al-Muhandis, deputy chief of Iraq's paramilitary Hashd Shaabi forces, instantly inflaming the already strained Washington-Tehran tensions.
Iran's Supreme Leader Ayatollah Ali Khamenei and President Hassan Rouhani have vowed to retaliate against the United States over Soleimani's death.
Rouhani said Saturday that the United States will pay a heavy price for assassination of Soleimani, official IRNA news agency reported.
"Americans have taken a new approach that could put the region in a very dangerous situation," Rouhani said.
The move was the culmination of tensions between the two countries since 2018, when Trump pulled out of the Iran nuclear deal and reimposed sanctions against Iran.
As the risk of further violence between the United States and Iran looms large, the international community is calling for utmost restraint to avoid further escalation of tensions in the Gulf.
UN Secretary-General Antonio Guterres on Friday called for "maximum restraint" by all related parties, saying the world cannot afford "another war in the Gulf."
Chinese State Councilor and Foreign Minister Wang Yi exchanged views and coordinated stances with Russian Foreign Minister Sergei Lavrov in a phone call late Saturday over the escalating tensions in the Gulf region.
Wang said that China pays high attention to the intensification of U.S.-Iran conflict, opposes the abuse of force in international relations, and holds that military adventures are unacceptable.
For his part, Lavrov said that Russia shares the same position with China, adding that the U.S. actions are illegal and should be condemned.
During another phone conversation with French Foreign Minister Jean-Yves Le Drian, Wang said unilateral use of force will not solve any problem but only backfire and lead to a vicious circle of confrontation.
Le Drian stressed that France opposes the use of force in international relations and Iraq's territorial sovereignty should be respected.
It is vital to preserve the Iran nuclear deal under the current circumstance, Le Drian said, adding that the French side hopes to stay in close communication with China and play a positive role in preventing the escalation of regional tensions.
The Iranian-backed Iraqi Shiite militia Kata'ib Hezbollah (KH) on Saturday warned the Iraqi security forces to move away from the U.S. bases and keep a distance of no less than 1,000 meters as of Sunday.
The United States has urged its citizens in Iraq to leave "immediately," and the NATO suspended training mission in Iraq.
Trump warned Iran on Saturday that America has targeted 52 Iranian sites and Iran will be hit "VERY FAST AND VERY HARD" if it attacked any American or U.S. assets.
Major cities in America, including Washington, New York and Los Angeles, are on alert after the deadly incident while local authorities said there is no credible or specific threats toward the cities.
Meanwhile, anti-war protests took place across the United States on Saturday.
In Times Square of New York City, many protesters held signs that read "Jobs, healthcare, education, housing, human needs, not endless war," and "No war/sanctions on Iran!"
"For all who believe in peace, for all who are opposed to yet another catastrophic war, now is the time to take action," a coalition known as ANSWER, for Act Now to Stop War and End Racism, said in a statement.