Two Katyusha rockets were fired at Ain al-Assad airbase. An Iraqi security source said the rockets fell inside the base.

At least five US personnel were injured in an attack against a military base in Iraq, US officials have said, amid rising tensions following last week’s killing of senior members of Hamas and Hezbollah.

Two Katyusha rockets were fired at the Ain al-Assad airbase in western Iraq on Monday, two Iraqi security sources told the Reuters news agency. One of the Iraqi sources said the rockets fell inside the base. It was unclear whether the attack was linked to threats by Iran to retaliate over the killing of the Hamas leader.

The US officials, who spoke to Reuters on condition of anonymity, said one of the Americans was seriously injured. The Associated Press news agency, meanwhile, citing US defence officials, said that as many as seven military personnel and civilians were hurt.

The White House said the president and vice president had been briefed on the attack.

“Base personnel are conducting a post-attack damage assessment,” one of the officials told Reuters. Ismail Haniyeh, the political leader of the Palestinian group Hamas, was assassinated in the Iranian capital Tehran last week, an attack that drew threats of revenge by Iran. Iran has blamed Israel for the killing, but Israel has not claimed responsibility.

Adding to tensions, an Israeli strike on Beirut last week also killed Fuad Shukir, the senior commander of the Lebanese group Hezbollah.

Iran has said the United States bears responsibility for the assassination of Haniyeh because of its support for Israel.

US deploys military forces anticipating retaliatory threats

In a call on Monday, US Secretary of Defense Lloyd Austin and Israeli Minister of Defence Yoav Gallant agreed that the attack marked “a dangerous escalation”, according to a Pentagon read-out.

Last week the US carried out a strike in Iraq against individuals US officials said were “militants” getting ready to launch drones and posed a threat to US and coalition forces.

The US has been watching for Iran’s response to the killing of Haniyeh in Tehran.

Following the assassination, the US sent additional military forces to the Middle East in anticipation of retaliatory attacks, describing the deployment as “defensive”.

The nearly 10-month-old war in Gaza between Israel and Hamas has led to regular low-level hostilities between Israel and Iran and Hezbollah, as well as other groups in the region that are aligned with Tehran.

It is widely thought that neither side is ready for an all-out war, but the heightened tensions mean the risk of a conflagration is high.

A rare ally of both the US and Iran, Iraq hosts 2,500 US soldiers and has Iran-backed fighter groups linked to its security forces. The country has witnessed escalating tit-for-tat attacks since the Gaza war erupted in October.