"Rockets were launched at Ain al-Assad base" in Anbar province, said the military source.

While some "fell inside the base", one rocket landed on a nearby village without causing any damage, the source added.

A commander in a pro-Iran armed group told AFP that at least "two rockets targeted" the base, without saying who had carried out the attack.

Another source in the group and a security source confirmed an attack occurred.

All sources spoke on condition of anonymity because they are not authorised to speak to the media.

Such attacks were frequent early in the war between Israel and Hamas Palestinian militants in Gaza but since then have largely halted.

But the latest rocket fire comes as fears grow of an attack by Iran and its allies on Israel in retaliation for the killing of top Hamas and Hezbollah figures in strikes last weeks either blamed on or claimed by Israel.

The killings, with both Iran and Hezbollah vowing retaliation, are among the most serious series of tit-for-tat attacks that had already heightened fears of a regional conflagration stemming from the Gaza war.

The Iran-aligned "Axis of Resistance" against Israel, which also includes Iraqi groups and Yemen's Huthis, have already been drawn into the nearly 10-month war.

- Talks -

Monday's rocket attack also occurred after US forces carried out an air strike Tuesday night on pro-Iran Iraqi fighters who were attempting to launch drones that were deemed a threat to American and allied troops, a US official said.

The strike, which Iraqi sources said left four killed, was the first by American forces in Iraq since February.

There have been two recent attacks targeting bases hosting US and allied forces in Iraq -- on July 16 and 25. The troops are part of an anti-jihadist coalition.

Prior to that, US troops in Iraq and Syria had not been targeted since April. But attacks against them were much more common in the first few months of the Israel-Hamas war in Gaza, when they were targeted more than 175 times.

The Islamic Resistance in Iraq, a loose alliance of pro-Iran groups, claimed the majority of the attacks, saying they were in solidarity with Palestinians in Gaza.

In January, a drone strike blamed on those groups killed three US soldiers at a base in Jordan. In retaliation, US forces launched dozens of strikes against Tehran-backed fighters in Iraq and Syria.

Since then, attacks against US troops have largely halted.

Baghdad has sought to defuse tensions, engaging in talks with Washington on the future of the US-led coalition's mission in Iraq, with Iran-backed groups demanding a withdrawal.

The US military has around 2,500 troops in Iraq and 900 in Syria.