Members of the Iraqi rapid response forces fire a missile toward Daeh militants during a battle in Somer district of eastern Mosul, Iraq. Image Credit: Reuters

Baghdad: A senior US military official said on Wednesday attacks by Iranian-backed groups on bases hosting US forces in Iraq were gathering pace and becoming more sophisticated, pushing all sides closer to an uncontrollable escalation.

His warning came two days after four Katyusha rockets struck a base near Baghdad international airport, wounding five members of Iraq’s elite Counter-Terrorism Service.

It was the latest in a spate of rocket strikes in the past five weeks on military installations hosting members of the US-led coalition whose objective is to defeat Daesh insurgents.

The official said the attacks were jeopardising the coalition’s ability to combat Daesh insurgents.

Tension between the United States and Iran has ramped up in the region over US economic sanctions that are hitting Tehran hard.

The two sides have traded blame over attacks on oil installations, militia arms depots as well as military bases hosting US forces.

“We’re used to harassing fire,” said the military official, who spoke on condition of anonymity.

“But the pace of (that) was (previously) pretty episodic ... (Now) the level of complexity is increasing, the volume of rockets being shot in a single volley is increasing and is very concerning to us.”

The official added: “There is a point at which their actions change things on the ground and make it more likely that some other actions, some other choices made by somebody, whether it’s them or us will escalate unintentionally.”

The military official said Iranian-armed militias were approaching a red line where the coalition would respond with force, and “no one will like the outcome”.

There have been no claims of responsibility for any of the attacks. However the US military official said intelligence and forensic analyses of the rockets and launchers pointed to Iranian-backed Shiite militia groups, notably Kataib Hezbollah and Asaib Ahl al-Haq (AAH).

Iraqi paramilitary groups have in turn accused the United States and Israel of bombing their weapons depots and bases.

Most of Iraq’s Shiite militia groups are part of the Popular Mobilization Forces (PMF), an umbrella that has allies in parliament and government.

They report to the prime minister but have their own command structure outside the military.