A senior advisor to Leader of the Islamic Revolution Ayatollah Seyyed Ali Khamenei says if the United States continues to keep its forces in the Middle East, the region will turn into a new Vietnam for Washington.

"Americans took a foolish move by assassinating him and they must leave the region,” said Ali Akbar Velayati, speaking at a commemoration ceremony held on Sunday for the late Iranian military commander, Lieutenant General Qassem Soleimani and his companions, including Abu Mahdi al-Muhandis, the deputy chief of Iraq's Popular Mobilization Units (PMU).

“If they [Americans] do not leave the region, they will face another Vietnam [in the Middle East],” Velayati said, adding, "Experience has shown that they have been always defeated in the face of plans made by Iran and the axis of resistance.”

The assassination of the two commanders at Baghdad airport in the early hours of Friday has triggered a wave of rage among Iranians and Iraqis, and forged an unprecedented unity with vociferous calls for revenge.

Both Soleimani and Muhandis were popular figureheads in helping squelch an ominous rise of Daesh, which once came as close as 30 kilometers to Baghdad, while the US withdrew troops from Iraq and looked on.

In all, 10 people -- five Iraqis and five Iranians -- were assassinated in the US strike on their motorcade just outside Baghdad airport early Friday as Gen. Soleimani’s flight arrived from Syria, leading to speculations that the Israeli intelligence might have played a role.

The Pentagon said in a statement that US President Donald Trump had ordered the military to assassinate the Iranian commander.

The assassination prompted calls for revenge from various resistance groups across the region with Iranian officials also vowing crushing response to the US act of terrorism. Informed military sources told Press TV that the United States has started pulling its troops out of the region since Saturday, despite claims to the contrary.

Elsewhere in his remarks, Velayati said a recent joint naval maneuver with the participation of Iran, Russia and China was a "turning point" in the region.

"Despite Trump's foolish rants, Iran will act in a way that will make the US regret" any acts of foolishness.

Late last month, Iran, Russia and China held three days of joint maritime exercise, dubbed as the "Marine Security Belt", in an area of 17,000 square kilometers in the Indian Ocean and the Sea of Oman area which consist of "various tactical exercises", such as target practicing and rescuing ships from assault and incidents such as fires.

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In response to a question raised by the Islamic Republic of Iran Broadcasting (IRIB) about Trump's threat to strike 52 important sites in Iran, Velayati said,"The Iranian nation has shown through history that it will put any aggressor in its place and any aggressor who dares to do this will regret it."

In a Saturday tweet, the White House tenant claimed that the US military would hit “very important” targets related to Iran if the Islamic Republic seeks retaliation.

“… we have … targeted 52 Iranian sites (representing the 52 American hostages taken by Iran many years ago), some at a very high level & important to Iran,” Trump tweeted, making a reference to the 1979 US embassy incident in Tehran.

In reaction to Trump's “hostile” remarks, Iranian Deputy Foreign Minister for Political Affairs Abbas Araqchi said earlier on Sunday that such threats clearly amount to war crime according to international law.

Araqchi summoned the Swiss ambassador, whose country represents Washington’s interests in Iran, to convey the Islamic Republic’s firm dismissal of Trump’s threatening language by describing his latest anti-Iran threats as “utterly unacceptable and unconventional.”