WASHINGTON — The U.S. military carried out "precision defense strikes" in Iraq and Syria against a militia group following a string of attacks on Iraqi bases that host American servicemembers.

"In response to repeated Kata'ib Hizbollah (KH) attacks on Iraqi bases that host Operation Inherent Resolve coalition forces, U.S. forces have conducted precision defensive strikes against five KH facilities in Iraq and Syria that will degrade KH's ability to conduct future attacks against OIR coalition forces," chief Pentagon spokesman Jonathan Hoffman said in a statement Sunday.

"Iran and their KH proxy forces must cease their attacks on U.S. and coalition forces, and respect Iraq's sovereignty, to prevent additional defensive actions by U.S. forces," Hoffman added.

The Pentagon said in a statement that three locations in Iraq and two in Syria were targeted by U.S. forces. The locations included weapon storage facilities and command and control locations that the Iranian-backed Shi'ite Muslim militia uses to plan and execute attacks on OIR coalition forces. It was not immediately clear what U.S. military assets were used in the strikes.

The U.S. military action comes on the heels of recent Kata'ib Hezbollah strikes on Iraqi military bases that host American troops. On Friday a U.S. civilian contractor was killed in a rocket attack on an Iraqi base near Kirkuk.

Earlier this month, Secretary of State Mike Pompeo blamed Iranian-backed forces for a series of attacks on bases in Iraq and warned that any future attacks on Americans or U.S. allies would be "answered with a decisive U.S. response."

"As long as its malign behaviors continue, so will our campaign of maximum pressure," Pompeo said during a December 11 press conference at the State Department.

Pompeo then announced another round of fresh sanctions on Tehran, this time targeting Iran's largest shipping company and biggest airline, saying the companies are aiding the Iranian regime's alleged proliferation of weapons of mass destruction.

The latest action represents another brick in the crumbling edifice between Washington and Tehran after a string of attacks in the Persian Gulf this summer.

In June, U.S. officials said an Iranian surface-to-air missile shot down an American military surveillance drone over the Strait of Hormuz. Iran said the aircraft was over its territory.

That strike came a week after the U.S. blamed Iran for attacks on two oil tankers in the Persian Gulf region and after four tankers were attacked in May.