Hundreds of Iraqis protesting the Israel-Iran attack on Iran that killed supreme leader Ayatollah Ali Khamenei gathered near Baghdad's Green Zone, where the US embassy is located.

Dozens tried to storm the fortified area, which also hosts key government buildings, but security forces dispersed them, mainly with tear gas.

It was their second attempt on Sunday to enter the area after clashing in the morning with heavily deployed security forces.

An AFP photographer saw ambulances arriving at the evening gathering and reported cases of suffocation from tear gas and hearing what sounded like live gunfire.

The Iraqi government's security media cell said some demonstrators shot at security forces and set vehicles on fire, injuring security personnel who were taken to the hospital.

The unit said security forces "did not resort to using firearms despite coming under fire," and that three people involved in the shooting were arrested.

A health official in Baghdad told AFP that four people with gunshot wounds were transferred to a hospital and that 66 people suffered from suffocation due to tear gas.

The US embassy had warned earlier that protests near its compound "may turn violent," and advised its nationals to "remain alert to their surroundings and avoid large crowds."

It also warned of "active threats to US interests in Iraq including restaurants, businesses, and individuals."

Telegram channels and social media platforms close to pro-Iran armed groups called on people to take part in the protests.