The United States on Sunday carried out airstrikes targeting Iran-backed militias in Iraq and Syria, in response to drone attacks by the militias on U.S. personnel and facilities in Iraq, according to the Pentagon.

The strikes targeted “operational and weapons storage facilities” at two locations in Syria and one in Iraq, all of which lie in the border region between the two countries, according to a Defense Department statement. The facilities were used by several Iran-backed militia groups, according to the Pentagon, including Kata’ib Hezbollah and Kata’ib Sayyid al-Shuhada.

“As demonstrated by this evening’s strikes, President Biden has been clear that he will act to protect U.S. personnel,” and has authorized further military action to “deter and disrupt” such attacks on U.S. forces, said the statement.

The Pentagon emphasized that the strikes were defensive in nature, as well as “appropriately limited in scope.”

There were no reports of casualties from the airstrikes, but officials said assessments were ongoing, according to Reuters.

Since April, Iran-backed militias have carried out “at least five” drone attacks against facilities used by U.S. and coalition personnel, said Reuters, citing two anonymous U.S. officials.

One of the three facilities targeted by the U.S. strikes had been used to launch and recover the drones, according to the report.

This was the second round of strikes ordered by Biden on Iran-backed militias since he took office in January. On Feb. 25, the U.S. military struck multiple targets in eastern Syria, in response to a Feb. 15 rocket attack on Iraq’s Erbil International Airport that killed a civilian contractor working with the U.S.-led military and injured several others, including an U.S. service member.