"We are sending additional forces to support our personnel at the Embassy," said Esper in a statement, without providing any detail about the number of forces to be deployed.

Esper also called on the Iraqi government to shoulder its international responsibility of protecting the US personnel in the country.

Earlier in the day, hundreds of demonstrators, participating in mourning for the Hashd Shaabi members killed by a US attack in Iraq on Sunday, stormed the U.S. Embassy in Baghdad's Green Zone.

Some protesters smashed one of the gates and broke into the outer yards of the embassy, sparking a clash with the guards who fired tear gas canisters against the demonstrators, an official from the Iraqi Interior Ministry told Xinhua on condition of anonymity.

US President Donald Trump blamed Iran for "orchestrating an attack" on the embassy in a Tuesday morning tweet.

US forces on Sunday attacked five locations in Iraq and Syria controlled by Iraq's paramilitary Kata'ib Hezbollah (KH), or Hezbollah Brigades, in response to recent attacks on US forces in Iraq, triggering strong responses from Iraq and Syria, with Iran denying any role in the recent attacks on US forces in Iraq.

Hashd Shaabi, an Iraqi state-sponsored umbrella organization, was formed by the KH and other Shia Iraqi paramilitary groups in 2014. It currently includes more than 40 militant groups.