There was no immediate claim of responsibility.

A US military official speaking on condition of anonymity told AFP that alarms had gone off and that "likely impact sounds" could be heard near the US embassy and Union III base, where troops from the international anti-jihadist coalition are stationed.

This is the first reported attack against the United States embassy in the Iraqi capital since the Israel-Hamas war began in early October, raising regional tensions and fears of a wider conflict.

Since mid-October there have been dozens of rocket or drone strikes by pro-Iran groups against American or coalition forces elsewhere in Iraq as well as in Syria.

There are roughly 2,500 US troops in Iraq and about 900 in Syria as part of efforts to prevent a resurgence of the Islamic State group.

At around 4:20 am (0120 GMT), "three Katyusha rockets targeting the American embassy fell close to the Green Zone, near the river" Tigris, the Iraqi security official told AFP. The Iraqi official spoke on condition of anonymity as he was not authorised to speak to the media.

The US official said: "We are still awaiting official reports regarding casualties and damage to infrastructure, if any. We are also awaiting official reporting on the type of attack."

After the end of a seven-day pause in the war between Israel and Iran-backed Hamas last week, pro-Iran groups have resumed their attacks against American and coalition forces, justifying their actions by pointing to Washington's support for Israel.

- Around 80 attacks -

In Iraq, most were claimed by the Islamic Resistance in Iraq, a loose formation of armed groups affiliated with the Hashed al-Shaabi coalition of former paramilitaries who are now integrated into Iraq's regular armed forces.

US forces have struck Iran-linked targets in both Iraq and Syria in response.

On Sunday a US military official speaking on condition of anonymity confirmed a "self-defence strike" was carried out in northern Iraq against a drone launch site "in the vicinity of Kirkuk" against "an imminent threat".

The Islamic Resistance in Iraq later announced the death of "five martyrs".

That strike came a day after Iraqi Prime Minister Mohammed Shia al-Sudani said during a phone call with US Secretary of State Antony Blinken that Baghdad rejected "any attack on Iraqi territory", according to a statement from Sudani's office.

Sudani also said the Iraqi government is committed "to ensuring the safety of the international coalition advisers present in Iraq".

On Wednesday, a US military official said a drone had targeted Western troops at the Ain al-Asad Airbase in western Iraq, but there were no casualties or damage.

In total, Washington has counted at least 78 attacks since October 17 against its forces in Iraq and Syria, 10 days after the start of the war between Israel and Hamas.

The Israel-Hamas war began with the Palestinian militant group's unprecedented attack on Israeli soil, which killed around 1,200 people and saw about 240 people captured as hostages, according to Israeli officials.

In response, Israel vowed to destroy Hamas, with bombardments and a ground offensive that have killed 17,177 people, Hamas authorities in Gaza said.

The attacks against US personnel included rocket fire and drone strikes, and have left at least 60 US personnel wounded, the Pentagon says.