A rocket was fired at the headquarters of global oil companies, including U.S. energy giant ExxonMobil, near Iraq’s southern city of Basra early on Wednesday, raising alarm amid rising tensions between the United States and Iran.

The rocket targeted the headquarters of the Iraqi Drilling Company in the Burjesia site west of the city, according to a company spokesperson. Burjesia is also used as a base by Royal Dutch Shell PLC and Eni.

A second rocket that landed in a nearby area did not explode. Three Iraqi workers were wounded in the attack, local police said. There was no immediate claim of responsibility.

However, an Iraqi security source said it appeared that Iranian-sponsored militia groups in southern Iraq were behind the Basra incident. “According to our sources, the team (that launched the rocket) is made up of more than one group and were well trained in missile launching,” he explained.

The mayor of the nearby town of Zubair, Abbas Maher, said he believed “groups linked to regional powers,” a reference to Iran, had hit ExxonMobil to “send a message” to the United States.

“We cannot separate this from regional developments, meaning the U.S.-Iranian conflict,” Maher observed. “These incidents have political objectives (…) it seems some sides did not like the return of Exxon staff.”

The attack was one of several such incidents in the past week on Iraqi bases housing U.S. military personnel. Three Katyusha rockets were fired at the Taji joint U.S.-Iraqi base north of Baghdad, while another rocket hit a U.S.-Iraqi training base in the city of Mosul late on Tuesday.

Last month, a rocket was fired into Baghdad’s Green Zone in the first such attack since September 2018, when three mortar shells landed in an abandoned lot inside the heavily fortified government district.

The rocket was believed to have been fired from east Baghdad – an area controlled by Iranian-sponsored militia forces. The Katyusha rocket exploded near the statue of the Unknown Soldier, less than one mile from the U.S. Embassy.