US forces came under attack at least four more times by Iran-backed groups in Syria after the US military carried out air strikes on targets associated with Iran’s Islamic Revolutionary Guard corps on Sunday, a US official told CNN.

All four of the attacks came after the US struck a training facility and safe house on Sunday near the cities of Abu Kamal and Mayadin, respectively. The Pentagon is not currently tracking any injuries or damage from the four latest attacks.

“The President has no higher priority than the safety of US personnel, and he directed today’s action to make clear that the United States will defend itself, its personnel, and its interests,” Defense Secretary Lloyd Austin said of the US strikes on Sunday.

Sunday’s strikes mark the third time the US has attacked facilities or targets in the region after continued attacks on US and coalition forces in Iraq and Syria. Last Wednesday, two US F-15 fighter jets struck a weapons storage facility used by the IRGC and affiliated groups. And on October 26, the US struck two facilities linked to Iranian-backed militias.

The latest attacks mark at least 50 that have targeted US forces in the region since October 17. At least 56 troops have been injured in those attacks — at least 25 have sustained traumatic brain injuries, while other injuries have been minor, Pentagon officials have said.

On Sunday, a second defense official said that the training facility was believed to also be functioning as a logistics and weapons storage facility “based on the secondary explosions observed following the strikes.” The safe house near Mayadin was assessed to be functioning as a headquarters facility for IRGC-affiliated groups in the area, the official said.

“This operation was intended to disrupt and degrade the freedom of action and capabilities of IRGC and affiliated forces directly responsible for attacking US forces,” the official added.

The official also said that IRGC-related militia personnel were present at the facilities when they were hit, though they said they are “unable to provide a casualty assessment at this time.”

“The United States does not seek conflict and has no desire to engage in further hostilities, but these Iran-backed attacks against US forces are unacceptable and must stop,” the official said. “We specifically targeted IRGC-associated facilities to make clear to Iran that we will hold them responsible for these attacks against US forces.”