Protesters set fire to a guard room outside the U.S. embassy in Baghdad, Iraq on Dec. 31, 2019. (Xinhua/Khalil Dawood)

Hundreds of demonstrators on Tuesday stormed and set fire to the U.S. embassy in Iraq's capital Baghdad during their mourning for the Hashd Shaabi members killed by a U.S. bombardment in Iraq two days ago.

BAGHDAD, Dec. 31 (Xinhua) -- Hundreds of demonstrators, participating in mourning for the Hashd Shaabi members killed by U.S. attack in Iraq, stormed the U.S. embassy in Baghdad's Green Zone on Tuesday, a security official said.

Many of the protesters, wearing Hashd Shaabi's military uniforms, rallied outside the embassy chanting slogans condemning airstrikes by the U.S. forces against Hashd Shaabi bases in Iraq.

The protest then turned violent as protesters set ablaze a guard tower and the outer gate of the embassy, an official from the Iraqi Interior Ministry told Xinhua on condition of anonymity.

Protesters try to set fire to the outside fence of the U.S. embassy in Baghdad, Iraq on Dec. 31, 2019. (Xinhua/Khalil Dawood)

Afterwards, the protesters managed to broke into an outer yard of the embassy, but were repelled by the security forces who deployed tear gas against them, the source said.

The clash left some 20 protesters wounded and suffocated, according to a statement by the Hashd Shaabi website.

The demonstrators later set up tents in front of the entrance of the U.S. embassy for a sit-in protest, while some of them wrote on the wall of the embassy "closed in the name of the people."

Protesters gather in front of the U.S. embassy in Baghdad, Iraq on Dec. 31, 2019. (Xinhua/Khalil Dawood)

Local media aired photos showing Qais al-Khazali, head of Asa'ib Ahl al-Haq militia, and top Hashd Shaabi leader Hadi Al Amri and Abu Mahdi al-Muhandis participating in the protest.

Iraqi security forces then arrived at the scene.

The office of Iraqi caretaker Prime Minister Adel Abdul Mahdi, in a statement, called on the demonstrators to leave immediately, saying that "any attack on foreign embassies is an act that will be strictly prevented by the security forces, and will be punished severely by the law."

Another statement by the office said the prime minister declared a three-day mourning starting on Tuesday for the Hashd Shaabi members killed in the attack.

Protesters gather in front of the U.S. embassy in Baghdad, Iraq on Dec. 31, 2019. (Xinhua/Khalil Dawood)

Meanwhile, Jaafar al-Husseini, spokesman of Kata'ib Hezbollah (KH) militia told local media that the protesters had "no intention to attack the U.S. embassy, but the sit-in is to continue until the embassy is closed and the U.S. ambassador is expelled."

The protest came two days after the U.S. forces bombarded headquarters of Hashd Shaabi's 45th and 46th Brigades, leaving 25 killed and 51 injured.

A U.S. military statement said that U.S. forces attacked on Sunday evening five bases of KH in Iraq and Syria in response to repeated attacks by KH against U.S.-led coalition forces in Iraq. ■