WASHINGTON — US military forces carried out airstrikes in Iraq and Syria on Sunday against Iran-backed militia groups that were behind drone attacks on American personnel in Iraq.

The airstrikes come after US President Joe Biden directed military forces to conduct defensive precision airstrikes against facilities used by Iran-backed militia groups in the Iraq-Syria border region on Sunday evening, according to a press statement from the Department of Defense.

"The targets were selected because these facilities are utilized by Iran-backed militias that are engaged in unmanned aerial vehicle (UAV) attacks against US personnel and facilities in Iraq,” Pentagon press secretary John Kirby said in the statement.

“Specifically, the US strikes targeted operational and weapons storage facilities at two locations in Syria and one location in Iraq, both of which lie close to the border between those countries. The facilities were used by at least two militias, Kata'ib Hezbollah and Kata'ib Sayyid Al-Shuhada,” according to the statement.

The fourteenth brigade of the Popular Mobilization Units, an umbrella group for a number of Iran-backed militias in Iraq, said four of its fighters were killed in the attack. The fourteenth brigade is made up of Kata'ib Sayyid Al-Shuhada members.

"As demonstrated by this evening's strikes, President Biden has been clear that he will act to protect US personnel. Given the ongoing series of attacks by Iran-backed groups targeting US interests in Iraq, the President directed further military action to disrupt and deter such attacks," Kirby added in the statement.

House Speaker Nancy Pelosi said in a statement Sunday evening that the airstrikes "appear to be a targeted and proportional response to a serious and specific threat."

"Protecting the military heroes who defend our freedoms is a sacred priority. The Iran-backed militias utilizing these facilities have been engaged in attacks threatening US servicemembers, as well as our allies," she said.

"Congress looks forward to receiving and reviewing the formal notification of this operation under the War Powers Act and to receiving additional briefings from the Administration."