The number of injured continues to climb after Iran-backed militias killed three U.S. service members and injured dozens more in an overnight attack on a military base in northeast Jordan. 

By late Sunday, the number of injured had climbed to 34 service members. This included at least eight personnel whose injuries warranted an evacuation from Jordan to higher-level care, though they were believed to be in stable condition. 

Fox News is told all service members are being fully evaluated for follow-on care. The number of injured was expected to fluctuate. 

The injuries mostly include traumatic brain injury, though the number of cases will likely go up as symptoms can take time to develop. 

IRAN-BACKED MILITIA KILLS 3 US TROOPS JUST WEEKS AFTER BIDEN SAID TEHRAN KNOWS ‘NOT TO DO ANYTHING’

Militant groups targeted the logistics support base located at Tower 22 of the Jordanian Defense Network. There are around 350 U.S. Army and Air Force personnel deployed at the base to counter ISIS. 

Out of respect for their families and per Defense Department policy, the identities of the service members are being withheld until 24 hours after their next of kin have been notified. 

The fatalities marked a major escalation after months of strikes by such groups against American forces across the Middle East since the start of the Israel-Hamas war.

Later Sunday, President Biden said that the U.S. "shall respond" to the attacks. In a written statement, Biden said the U.S. "will hold all those responsible to account at a time and in a manner (of) our choosing."

Defense Secretary Lloyd Austin said, "we will take all necessary actions to defend the United States, our troops, and our interests."