The U.S. attacked a key Yemen oil port controlled by the Houthis overnight and killed dozens of people, according to the Iran-backed militants, raising the specter of a widening conflict in the Middle East.

The assault on the Ras Issa fuel-import terminal appeared to be one of the biggest and deadliest since U.S. President Donald Trump ordered an aerial campaign against the Houthis in mid-March. The strikes have so far failed to stop Houthi maritime assaults in the Red Sea and missile attacks on Israel, causing the American military to consider supporting a ground offensive on the group by Yemeni factions.

Ras Issa, located about 60 kilometers (37 miles) north of the Red Sea city of Hodeida, was hit more than a dozen times by U.S. fighter jets. At least 74 people, most of them port workers, were killed and 171 were injured, according to Houthi-controlled health authorities in the area. Ras Issa, the main gateway for fuel coming into Houthi-held territory, suffered huge damage, the group said.