Washington/Baghdad: US President Donald Trump ordered the killing of Iran Revolutionary Guards commander Qasem Soleimani, who died in Baghdad "in a decisive defensive action to protect US personnel abroad," the Pentagon said Thursday.

"General Soleimani was actively developing plans to attack American diplomats and service members in Iraq and throughout the region. General Soleimani and his Quds Force were responsible for the deaths of hundreds of American and coalition service members and the wounding of thousands more," the Department of Defense said.

Following Soleimani's death, Trump tweeted an image of the US flag without any further explanation.

Officials said the strike also killed Abu Mahdi al-Muhandis, the deputy commander of Iran-backed militias known as the Popular Mobilization Forces.

An official with an Iran-backed paramilitary force said Friday that seven people were killed by a missile fired at Baghdad International Airport, blaming the United States.

The official with the group known as the Popular Mobilization Forces said the dead included its airport protocol officer, identifying him as Mohammed Reda.

A security official confirmed that seven people were killed in the attack on the airport, describing it as an airstrike. Earlier, Iraq’s Security Media Cell, which releases information regarding Iraqi security, said Katyusha rockets landed near the airport's cargo hall, killing several people and setting two cars on fire.

The security official said the bodies of those killed in the airport attack Friday were burned and difficult to identify. The official added that Reda may have been at the airport to pick up a group of “high-level” visitors who had arrived from a neighboring country. He declined to provide more information.

The attack came amid tensions with the United States after a New Year's Eve attack by Iran-backed militias on the US Embassy in Baghdad. The two-day embassy attack which ended Wednesday prompted Trump to order about 750 US soldiers deployed to the Middle East.

The breach at the embassy followed US airstrikes on Sunday that killed 25 fighters of the Iran-backed militia in Iraq, the Kataeb Hezbollah. The US military said the strikes were in retaliation for last week’s killing of an American contractor in a rocket attack on an Iraqi military base that the US blamed on the militia.

US officials had earlier suggested they were prepared to engage in further retaliatory attacks in Iraq.

“The game has changed,” Defense Secretary Mark Esper said Thursday, telling reporters that violent acts by Iran-backed Shiite militias in Iraq — including the rocket attack on Dec. 27 that killed one American — will be met with US military force.

He said the Iraqi government has fallen short of its obligation to defend its American partner in the attack on the US embassy.

The developments also represent a major downturn in Iraq-US relations that could further undermine US influence in the region and American troops in Iraq and weaken Washington’s hand in its pressure campaign against Iran.