As a military offensive by Turkey into Syria enters its third day, aid agencies are increasingly concerned. An estimated 100,000 civilians in northeastern Syria have been displaced, at least one displaced-persons camp was relocated out of the line of fire, a front-line hospital was abandoned and critical water infrastructure was taken out of commission, according to the United Nations. All of this is exacerbating a humanitarian crisis that was already one of the world's worst.

On Wednesday, Turkish ground and air forces commenced a series of assaults against a Syrian militia of the Kurdish ethnic group, which had been an American ally in the fight against ISIS but is viewed as a terrorist organization by the Turkish government.

Until this week, northeastern Syria near the border with Turkey had been a refuge of relative safety for people fleeing violence in other parts of the war-torn country. Humanitarian relief agencies have been providing food, water, medicine and other lifesaving aid to more than 90,000 internally displaced people there as well as more than 1 million other residents who had lost access to social services because of the conflict.

Now, the towns and camps where those people are living are suddenly on the front lines of a new, unpredictable combat operation.

On Friday, local Kurdish government officials announced plans to immediately evacuate 7,000 internally-displaced persons from one camp, al-Mabrouka, that they said had been hit with artillery shells. In the border town of Tal Abyad, hospital workers were forced to abandon at least one hospital because of shelling, according to Médecins Sans Frontières.

And according to UNICEF, a water pumping station that serves 400,000 people was attacked late Thursday and taken out of service.

"The situation on the ground is becoming increasingly dire, and once again, civilians are paying the highest price," Misty Buswell, Middle East policy director at the International Rescue Committee, said in a statement Friday afternoon. "There are already reports of [water] shortages in some rural areas, with possibly much worse to be seen in a few days if services are not able to get back up and running soon."

UNICEF, IRC, CARE International and some other groups have temporarily suspended services in the border area, evacuated foreign staff and asked local staff to remain home.

If humanitarian services continue to be cut off, the situation could quickly worsen, Karl Schembri, a spokesperson for the Norwegian Refugee Council, told NPR.

"These people are already under extreme duress," he says. "There are a lot of displaced-persons camps there that are completely dependent on aid services, and if they are cut off, that would put lives at immediate risk."

By Friday, Turkish troops had captured several Kurdish villages and blocked roads between others, The Associated Press reported. Riots broke out at Al-Hol, a camp near the border that was used to detain the wives and children of suspected Islamic State fighters.

Many of the displaced people are fleeing south, deeper into Syria, says Aleksandar Milutinovic, Syria country director for CARE. As the situation unfolds, it may become difficult to keep them from unintentionally winding up back in harm's way, squeezed between the Turkish offensive and the civil war.

"We're trying to understand where they can find safety," he says.

Meanwhile, Milutinovic says, humanitarian groups fear that the offensive could disrupt aid supply lines, which have been coming into Syria from Iraq.

"We really want to keep those lines open, so we don't face a shortage of food and other supplies," he says. "If the conflict continues, we expect those things will be depleted very fast. And we are very concerned about medical facilities. Unfortunately in any conflict zone, some doctors and medical employees have to leave, leaving very few resources to care for those people."

If and when the military campaign settles, there may be further humanitarian challenges ahead. Last month, Turkish President Recep Tayyip Erdoğan announced plans to return up to 2 million Syrian refugees currently living in Turkey to so-called "safe zones" in conquered territory in Syria. That plan was met with outcry from human rights advocates, who fear that such zones would be inaccessible to humanitarian workers and could become a backdrop for human rights violations by Turkish armed forces.

The plan "defies all norms of international law and humanitarian law, and it's outrageous," Stephen Morrison, director of the Global Health Policy Center at the Center for Strategic and International Studies, a Washington think tank. "And it's going to be a complete debacle for public health."

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