No targets were struck in Iran as many had called for.

These were only the first of retaliatory strikes and more will follow, the US has said.

The attacks followed the arrival of the bodies of the three American personnel killed in a drone strike by an Iran-backed group. President Joe Biden and First Lady Jill Biden joined the families at a military base in Delaware, his home state, for the dignified transfer as the solemn occasion is called. Although the strikes followed shortly after, news reports suggested they were not linked.

"This afternoon, at my direction, US military forces struck targets at facilities in Iraq and Syria that the IRGC and affiliated militia use to attack US forces," Biden said in a statement, referring to Iran's Islamic Revolutionary Guards Corps.

He added: "Our response began today. It will continue at times and places of our choosing."

The US President, who has been under mounting pressure internally to hit Iran, did not explain why the Friday airstrikes did not include targets in Iran, the US is unlikely to take that route because it does not want a war with Iran.

Defense Secretary Lloyd Austen said in a separate statement: "This is the start of our response. The President has directed additional actions to hold the IRGC and affiliated militias accountable for their attacks on US and Coalition Forces. These will unfold at times and places of our choosing."

The Central Command of the US military, which carried out the retaliatory attacks, said in a statement that 85 targets were hit and they included the IRGC’s Quds Force, which conducts unconventional warfare that includes running militias to serve its interests abroad. The US used long-range B-1 bombers aircraft that can carry a sizable volume and quantity of munition.

The Central Command said that the facilities that were struck included command and control operations centres, intelligence centres, rockets, missiles, unmanned aerial vehicle storage, and logistics and munition supply chain facilities of militia groups and their IRGC sponsors.