The attacks came as the US doubled down on its accusation that Iran was behind a series of operations against oil tankers in highly sensitive Gulf waters.

Baghdad fears a proxy conflict between the bitter enemies could play out in Iraq, where political and armed groups routinely accuse each other of being agents for foreign states.

Late Tuesday night, three rockets landed in the Rumailah oil field in Iraq's Basra, an industry source there said.

The rockets hit near a camp used by Baker Hughes, a company of US industrial conglomerate General Electric working in gas fields in Iraq, but did not cause any injuries, the source added.

It did however prompt US companies to issue emergency procedures to immediately evacuate senior-level foreign workers on the first flights out of Basra, the source said.

"There's a red alert issued by the American companies. The senior expat management are leaving today and tomorrow," the source told AFP, saying it was the same level of alert issued in May.

ExxonMobil withdrew its 83 expatriate workers from a nearby oil field in mid-May, but they returned after "guarantees" from the government.

"Since May, it had been about a year since anything similar had happened. It's not frequent," the source added.

A second industry source confirmed to AFP that "explosions" had been heard on Tuesday night near the Baker Hughes operation.

The associate head of the South Oil Company told local media rockets landed near a camp used by services company Oil Serv.

That camp also lies near the one used by Baker Hughes.

Hours later, around dawn on Wednesday, "a Katyusha rocket fell on an Iraqi drilling company in the Burjesiya area near Basra, wounding three people according to an initial assessment," Iraqi military command said in a statement.

Oil ministry spokesman Assem Jihad told AFP the wounded were all Iraqis and that the incident had "no impact on production".

Burjesiya is a complex near southern Iraq's main city, in a key oil-producing region hosting various Iraqi and foreign companies including US major ExxonMobil.

- Repeated rounds -

The oil-related incidents are only the latest in a string of rocket and mortar attacks on US interests.

On Friday evening, "three mortar rounds hit the Balad airbase (north of Baghdad), starting a fire," said the Iraqi military.

Then, on Sunday, rocket fire targeted the Baghdad military airport, a government source told AFP.

On Monday, three Katyusha rockets hit the Taji army base, which hosts both Iraqi and foreign troops, including Americans.

And on Tuesday, before the oil-related incidents, the Iraqi military announced an improvised rocket had hit a regional command base in the northern city of Mosul, where American troops are reportedly deployed.

No group has claimed the attacks, but experts say they appear to have been fired from Shiite-majority areas north of Baghdad.

That would appear to implicate pro-Iranian Shiite armed groups, as opposed to Sunni jihadists who continue to carry out hit-and-run attacks despite the elimination of the Islamic State group's "caliphate".

Prime Minister Adel Abdel Mahdi on Tuesday "ordered all forces to take all necessary measures" to prevent further rocket attacks.

"These actions disrupt the political situation and give a distorted picture of the security situation," he said.

bur-sbh/dv

EXXONMOBIL

GENERAL ELECTRIC

BAKER HUGHES