A commander from Kataib Hezbollah, an Iran-backed armed group in Iraq that the Pentagon has blamed for attacking its troops, was killed in a US strike on Wednesday, the US military said.

"(US) forces conducted a unilateral strike in Iraq in response to the attacks on US service members, killing a Kataib Hezbollah commander responsible for directly planning and participating in attacks on US forces in the region," a statement from the military said. It did not name the commander.

Two security sources, speaking on condition of anonymity, said the commander was Abu Baqir al-Saadi, killed in a drone strike on a vehicle in eastern Baghdad.

One of the sources said three people were killed and that the vehicle targeted was used by Iraq's Popular Mobilization Forces (PMF), a state security agency composed of dozens of armed groups, many of them backed by Iran.

Three US troops were killed in January in a drone attack near the Jordan-Syria border that the Pentagon said bore the "footprints" of Kataib Hezbollah. The group then announced it was suspending military operations against US troops in the region.

Iran-backed militias have targeted US forces in Iraq and Syria more than 160 times since mid-October.

The US struck Iran-backed groups in Iraq and Syria last weekend in what it said was just the beginning of its response to the killing of the three US soldiers.

In January, a US drone strike killed a senior militia commander in central Baghdad, an attack Washington said came in response to drone and rocket attacks on its forces.

On Wednesday, Iraqi special forces were on high alert in Baghdad and further units were deployed inside the Green Zone housing international diplomatic missions including the US embassy, a security source said.