Baghdad: Two mortar rounds hit the Iraqi capital's Green Zone on Saturday and two rockets slammed into a base housing US troops a day after the US carried out an airstrike outside the airport here and killed Iranian commander Qasem Soleimani, top Iraqi paramilitary chief Abu Mahdi al-Muhandis and a clutch of other Iranian and Iraqi figures.
The attack has raised the spectre of wider conflict in the Middle East.
In Baghdad, mortar rounds on Saturday evening hit the Green Zone, the high-security enclave where the US embassy is based, security sources said. The Iraqi military said that one projectile hit inside the zone, while another landed close to the enclave.
A pair of Katyusha rockets then hit the Balad airbase north of Baghdad, where American troops are based, security sources and the Iraqi military said. Security sources there reported blaring sirens and said surveillance drones were sent above the base to locate the source of the rockets.
The US embassy in Baghdad as well as the 5,200 American troops stationed across the country have faced a spate of rocket attacks in recent months that Washington has blamed on Iran and its allies in Iraq.
One attack last month killed a US contractor working in northern Iraq, prompting retaliatory American air strikes that killed 25 hardline fighters close to Iran.
Tensions boiled over on Friday when the US struck Soleimani's convoy as it drove out of the airport and US diplomats and troops across Iraq had been bracing themselves for more rocket attacks.
By ordering Friday's air strike on the commander of the Iranian Revolutionary Guard's foreign legions, President Donald Trump has taken Washington and its allies, mainly Saudi Arabia and Israel, into uncharted territory in its confrontation with Iran and its proxy militias across the region.
Gholamali Abuhamzeh, a senior commander of Iran's elite Revolutionary Guards, said Tehran would punish Americans "wherever they are in reach", and raised the prospect of possible attacks on ships in the Gulf.
The US Embassy in Baghdad urged American citizens to leave Iraq following the strike at Baghdad airport that killed Soleimani. Dozens of American employees of foreign oil companies left the southern Iraqi city of Basra on Friday.
Soleimani, a 62-year-old general, was Tehran's pre-eminent military commander and - as head of the Quds Force, the foreign arm of the Revolutionary Guards - the architect of Iran's spreading influence in the Middle East.
Muhandis was the deputy commander of Iraq's Popular Mobilisation Forces (PMF) umbrella body of paramilitary groups.
Trump said on Friday Soleimani had been plotting what he called imminent and sinister attacks on American diplomats and military personnel. Democratic critics of the Republican president said Trump's order was reckless and that he had raised the risk of more violence in a dangerous region.
On Friday, Iranian Supreme Leader Ayatollah Ali Khamenei vowed harsh vengeance against the "criminals" who killed Soleimani and said his death would intensify the Islamic Republic's resistance to the United States and Israel.
Abuhamzeh, the Revolutionary Guards commander in Kerman province, mentioned a series of possible targets for reprisals including the Gulf waterway through which a significant proportion of shipborne oil is exported to global markets.
Many Iraqis condemned the US attack, regarding Soleimani as a hero for his role in defeating the Islamic State militant group that had seized wide swathes of north and central Iraq in 2014.
Many Iraqis also voiced fear of being engulfed in a major US-Iranian conflict.
(With inputs from agencies)