The U.S. began striking targets tied to Iranian proxy groups in Iraq and Syria, U.S. officials told the Associated Press, after a deadly drone attack killed three American soldiers in Jordan last weekend.

The strikes started Friday afternoon shortly after the conclusion of a dignified transfer ceremony that honored the three fallen soldiers at Dover Air Force Base in Delaware, ABC News reported. President Joe Biden and Secretary of Defense Lloyd Austin attended the ceremony.

Earlier this week, the U.S. attributed responsibility for the Sunday drone attack to the Islamic Resistance in Iraq, an umbrella group of Iran-backed militias. Sgt. William Jerome Rivers, 46, Specialist Kennedy Ladon Sanders, 24, and Specialist Breonna Alexsondria Moffett, 23, died while based in Jordan. Roughly 40 other American service members were wounded.

The attack is the first that has resulted in the deaths of American soldiers since Iranian proxy groups started launching assaults on U.S. forces amid the geopolitical turmoil between Israel and Hamas since October 7.

Currently underway in Iraq and Syria, the retaliatory airstrikes come after Biden has been warning for days that the U.S. would forcefully respond to the attack. This latest wave of U.S. military action could further escalate tensions in the Middle East amid the Israel-Hamas war.

Iran has denied responsibility for the Jordan attack.