Iraqi security officials say a barrage of rockets has hit a base housing US troops in second attack this week.

The target was the American wing at the Taji military base, north of the Iraqi capital, although there was no immediate word on casualties, the Associated Press quoted security officials as saying.

The official said over a dozen rockets landed inside the base, some hitting the coalition quarters while others fell on a runway used by Iraqi forces.

An Iraqi colonel inside the base told Reuters news agency he heard at least 10 rockets hit the base and said he could now hear sirens blaring.

Last Wednesday, a rocket attack targeted an Iraqi base hosting troops from the international anti-ISIS coalition.

Two US and one British soldier were killed, and about 14 US-led coalition personnel were wounded, including Americans, Britons, Poles and others. Private industry contractors were among the wounded.

Britain identified the soldier killed as Lance Cpl Brodie Gillon, 26, a Reservist with the Scottish and North Irish Yeomanry.

US officials have accused Kataib Hezbollah, a sanctioned Shia Iraqi militia, as the culprit.

In retaliation, the US launched a series of airstrikes on militia bases across Iraq’s south, killing five Iraqi security forces and a civilian.

The civilians killed and wounded were construction workers at an airport building site in the Shiite holy city of Kerbala, Iraqi religious authorities said.

Iraq condemned the US air strikes on Friday, warning of dangerous consequences for what it called a violation of sovereignty and targeted aggression against the nation's regular armed forces.

President Barham Salih said repeated violations could cause Iraq to unravel into a failed state and revive ISIS.

Iraq's foreign ministry announced plans to bring a complaint to the United Nations and summoned the US and British ambassadors to the country for an explanation.

The US defended the air strikes, saying all five targets were legitimate and stored Iranian-supplied weapons used by the Kataib Hezbollah to attack the US-led coalition.

"These locations that we struck are clear locations of terrorist bases," said Marine Gen Kenneth McKenzie, head of the US military's Central Command.

"If Iraqis were there and if Iraqi military forces were there, I would say it's probably not a good idea to position yourself with Kataib Hezbollah in the wake of a strike that killed Americans and coalition members," he told a Pentagon news briefing.

Gen McKenzie acknowledged that a structure had been hit near the Kerbala airfield but said it was being used to store weapons.

"That was a clear target," he said.

Around 5,000 US troops remain in Iraq, most in an advisory capacity, as part of a wider international coalition formed to help Iraq drive back and defeat ISIS extremists.

But the Iraqi military said the new US air attack went against "any partnership" under the coalition. "It will have consequences that subject everyone to the most serious dangers."

Iran's foreign ministry said on Friday that the "presence and behaviour" of US and allied forces in Iraq was to blame for attacks against them.

Iranian-backed paramilitary groups have regularly rocketed and shelled bases in Iraq that host US forces and the area around the US Embassy in Baghdad.

Wednesday’s attack on Camp Taji was the deadliest to target US troops in Iraq since a late December rocket attack on an Iraqi base. That attack killed a US contractor and set in motion a series of tit-for-tat attacks that brought Iraq to the brink of war.

The American airstrikes targeting Kataib Hezbollah led to protests at the US Embassy in Baghdad in December.

A US drone strike in Baghdad then killed Iranian Gen Qassim Suleimani, a top commander responsible for expeditionary operations across the wider Mideast. Iran struck back with a ballistic missile attack on US forces in Iraq, the Islamic Republic’s most direct assault on America since the 1979 seizing of the US Embassy in Tehran.

In the retaliation, Iran shot down commercial Ukraine International Airlines flight 752, killing all 176 aboard.

The US and Iran stepped back from further attacks after the Suleimani incident. A senior US official said in late January, when US-Iran tensions had cooled, that the killing of Americans constituted a red line that could spark more violence.

But Iraq’s parliament also passed a resolution calling for all foreign troops to leave after Suleimani was killed. The recent air strikes could see those calls renewed.

Caretaker prime minister Adel Abdul Mahdi is one of those calling for US troops to withdraw.

But Gen McKenzie said he was confident the United States would be able to keep troops in Iraq.

He added that while the latest U.S. strikes would deter militia from waging similarly deadly rocket attacks, the risk from Iran and the groups it backs remained high.

Source: The National