The top U.S. commander in the Middle East said that a rocket attack on Camp Taji, Iraq, that killed two U.S. troops and a British medic was likely carried out by an Iranian-backed militia, and signaled Tehran's continuing activities aimed at driving the U.S. from the region.
Marine Gen. Frank McKenzie, head of U.S. Central Command, said the U.S. is still working to identify those responsible for Wednesday's attack on Camp Taji, which is located about 20 miles north of Baghdad.
"It was most likely a Shia group" supported by Iran, he added.
At a Senate Armed Services Committee hearing Thursday, McKenzie said that the Iranian-backed Kata'ib Hezbollah, part of Iraq's Popular Mobilization Forces (PMF), is the only group in his estimation capable of mounting the multiple rocket launches that hit Taji,
U.S. and British officials have pledged a response to the attack, but gave no indication of what form it might take.
"[The] deadly attack on Iraq's Camp Taji military base will not be tolerated," U.S. Secretary of State Mike Pompeo said on Twitter. He agreed with British Foreign Secretary Dominic Raab that "those responsible must be held accountable."
The identities of the three killed are being withheld until their families can be notified, but Britain's Ministry of Defense said the U.K. service member was from the Royal Army Medical Corps.
Syria's state-run Syrian Arab News Agency and the Syrian Observatory for Human Rights, a London-based monitoring group, reported airstrikes in eastern Syria near Al Bukamal, just across the Iraqi border, immediately after the Taji attack.
McKenzie made no mention of airstrikes in his testimony, and there was no immediate confirmation of airstrikes from U.S. or British officials.
The U.S. has blamed Katai'b Hezbollah for several previous rocket attacks on both Taji and Baghdad's "Green Zone," which houses the U.S. Embassy.
In a statement Wednesday night, Combined Joint Task Force-Operation Inherent Resolve said that 12 coalition personnel were wounded at Camp Taji, in addition to the three killed.
Taji is an Iraqi base that hosts U.S. and coalition personnel for train-and-advise missions.
About 18 of the 107mm Katyusha rockets struck the base in the attack. Iraqi security forces later found a truck rocket launcher a few miles from the base, according to the statement.
The attack came four days after the deaths of two Marine Raiders, Gunnery Sgt. Diego D. Pongo, 34, and Capt. Moises A. Navas, 34, in action against a suspected ISIS stronghold in Iraq's north central Makhmour Mountains.
The Katai'b Hezbollah figured in several attacks that led to a Jan. 3 U.S. drone strike at Baghdad's International Airport that killed Iranian Quds Force leader Qasem Soleimani.
On Dec. 26, rocket attacks blamed on Kataib Hezbollah hit an Iraqi compound near central Kirkuk and killed a U.S. defense contractor and wounded several U.S. troops. The U.S. responded with airstrikes on Iranian-backed militia positions on the Iraq-Syria border.
The airstrikes were followed by violent demonstrations in Baghdad and attempts to breach the gates of the U.S. Embassy on Dec. 31 and Jan. 1.
Soleimani was killed Jan. 3. On Jan. 8, Iran launched at least 12 ballistic missiles at the Al Asad Air Base in Iraq's Anbar province.
President Donald Trump said the next day that there appeared to be no injuries to U.S. troops in the Al Asad attack, but more than 100 have since been diagnosed with traumatic brain injury from the concussive effects of the blasts.
At Thursday's Senate hearing, Sen. Jack Reed, D-Rhode Island, the ranking member of the committee, said the Taji attacks "seem to challenge the notion that we've re-established deterrence with respect to Iran" and the Tehran regime's destabilizing activities in the region.
In response, McKenzie said there is "ample intelligence" to show that Iran's "malign activities" are continuing through proxy groups such as Kataib Hezbollah.
"They have stood their missiles down -- I don't think that's an imminent threat" since the Al Asad attack, he said, but added that the Iranian regime has "a continued desire to operate through their proxies against us."
-- Richard Sisk can be reached at Richard.Sisk@Military.com.