US President Joe Biden has ordered US defence forces to carry out another round of air strikes on weapons storage facilities in Iraq and Syria.

In a Pentagon statement, the US military said it targeted operational and weapons storage facilities at two locations in Syria and one location in Iraq, this time in response to drone attacks by the militia against US personnel and facilities in Iraq.

It did not disclose whether it believed anyone was killed or injured.

The strikes came at the direction of President Joe Biden, the second time he has ordered retaliatory strikes against Iran-backed militia since taking office five months ago.

“At President Biden’s direction, US military forces earlier this evening [Monday AEST] conducted defensive precision airstrikes against facilities used by Iran-backed militia groups in the Iraq-Syria border region.

“The targets were selected because these facilities are utilised by Iran-backed militias that are engaged in unmanned aerial vehicle (UAV) attacks against US personnel and facilities in Iraq,” the Pentagon statement read,” Pentagon Press Secretary John Kirby wrote.

Mr Biden last ordered limited strikes against a target in Syria in February, that time in response to rocket attacks in Iraq.

“As demonstrated by this evening’s strikes, President Biden has been clear that he will act to protect US personnel,” the Pentagon said.

The facilities targeted were used by Iran-backed militia, including Kataib Hezbollah and Kataib Sayyid al-Shuhada.

The strikes came even as Biden’s administration is looking to potentially revive a 2015 nuclear deal with Iran. The strikes appear to show Biden’s efforts to compartmentalise defensive strikes to protect American personnel, while simultaneously engaging Tehran in diplomacy.

His critics say Iran cannot be trusted and point to the drone attacks as further evidence that Iran and its proxies will never accept a US military presence in Iraq or Syria.

Mr Biden and the White House declined comment on the strikes on Sunday.

US officials believe Iran is behind a ramp-up in drone attacks and periodic rocket fire against US personnel and facilities in Iraq, where the US military has been helping Baghdad combat the remnants of Islamic State.

Two US officials, speaking to Reuters on condition of anonymity, said Iran-backed militias carried out at least five drone attacks against facilities used by US and coalition personnel in Iraq since April.

One of the facilities targeted was used to launch and recover the drones, a defence official said.

The US military carried out strikes with F-15 and F-16 aircraft, officials said, adding the pilots made it back from the mission safely.

“We assess each strike hit the intended targets,” one of the officials told Reuters.

Iraq’s government is struggling to deal with militias ideologically aligned with Iran which are accused of rocket fire against US forces and of involvement in killing peaceful pro-democracy activists.

-with agencies