Erbil, Iraq — An Iran-backed militia group in Iraq claimed responsibility Monday for a drone strike against a base in eastern Syria used by U.S. troops that killed six American-allied Kurdish fighters. The attack, which caused no American casualties, appeared to be the first significant response from what the U.S. calls Iran’s proxy groups to U.S. airstrikes against the militias in the region.

On Friday, the U.S. started striking the militias of an umbrella group known as the Islamic Resistance in Iraq in response to those groups’ stepped-up attacks on U.S. bases in the region — including the deadly drone strike on a base in Jordan that killed three U.S. service members on Jan. 28.

The Kurdish-led Syrian Democratic Forces said Monday that a drone struck a training ground the previous night at the al-Omar base in Syria’s eastern province of Deir el-Zour. The SDF trains commandos there, and some of the roughly 900 U.S. troops deployed in Syria as part of the ongoing mission against ISIS have been based there.

The Islamic Resistance in Iraq released a video claiming responsibility for the attack that included purported images of the drone being launched from an unspecified location.

With its strikes over the weekend against the militias in Iraq and Syria — and ongoing strikes against the Houthi rebels in Yemen who’ve been targeting ships in the Red Sea for months — the U.S. has continued its retaliation against Iran’s affiliates across a wide geographical area. All those groups say they’ve been attacking U.S. and Israeli interests in solidarity with Palestinians, as Israel continues its war against Hamas, which is also backed by Iran, in the Gaza Strip.

The U.S. and the U.K. launched strikes against 36 Houthi targets late Saturday, targeting missile launch and radar systems in the large portion of Yemen controlled by the Shiite Muslim rebels.

The Houthis’ slogan includes calls for “death to America” and “death to Israel.” The group vowed the strikes would “not go unpunished,” and just hours later, U.S. forces said they had hit several Houthi cruise missiles that were prepared to launch against ships in the Red Sea, where American military vessels are currently deployed.

The Houthis receive the bulk of their equipment and funding from Iran, according to the U.S. government.

The strike to take out the Houthi cruise missiles — one of several preemptive strikes in Yemen by U.S. and U.K. forces in recent weeks — came just a day after the U.S. said it had struck 85 targets in Iraq and across the border in Syria. Those strikes were retaliation for the deadly attack on the American soldiers just over a week ago in Jordan, and President Biden has vowed to continue retaliating against the militias as and when the U.S. military sees fit.

The U.S. has reported around 170 attacks against American forces in this region by Iran-backed groups since the Israel-Hamas war was ignited by the Palestinian militant group’s brutal Oct. 7 terror attack on southern Israel.

Iran has repeatedly denied any role in the increasing violence and when CBS News interviewed the country’s foreign minister in November, he rejected the notion of Iran having proxy groups and said the militias in Iraq and Syria attacking U.S. interests had “made their own decisions.”

Top officials in both the U.S. and Iran have said they don’t want the war between Israel and Hamas to widen and engulf the region. But the groups backed by Iran have vowed to continue retaliating against Israel and its closest ally, the U.S., for what they say is an unjust war in Gaza, and the U.S. has vowed to continue retaliating for any attacks by those groups that put Americans in harm’s way.

In addition to the roughly 900 American forces deployed in Syria, there are about 2,500 in Iraq. So, preventing any further escalation of the conflict in such a tense region with so many potential flashpoints will require a very delicate balance, in both words and actions.