IDLIB PROVINCE, Syria - Syrian civil defence volunteer Salam Mahmoud had only one thought when she saw the collapsed buildings after the devastating earthquake that struck Syria and Turkey.

"All I could think about was how can I get the children out? If there is someone alive, how can I reach them?," the 24-year-old said.

Mahmoud is one of around 300 women in the Syria Civil Defence, also called the White Helmets, a rescue service of more than 3,000 people which operates in insurgent-held northwestern Syria.

She said some people in the village of Millis, where she deployed the day of the disaster, objected at first to the sight of women taking part in rescue efforts.

"When we first got to the site... we were criticized a lot, and were told that we shouldn't have come down," she said, describing socially conservative views in the area about the role of women.

"But all of that shortly switched from negative to positive . We saved as many people as we could, met people's expectations and responded to women and children, who were under the rubble," she said.

Getting home that evening, Mahmoud said she couldn't sleep. "All night I was thinking: could there still be children calling for us, could there still be women screaming out."

The earthquake has killed more than 4,500 people in northwest Syria, according to local reports cited by the U.N. Office for the Coordination of Humanitarian Assistance. It killed more than 45,000 in neighbouring Turkey.

The Civil Defence rose to prominence by pulling people from under the rubble of buildings destroyed by air strikes and bombardment during the conflict that erupted in Syria in 2011.

Mahmoud has volunteered with the Civil Defence for five years. Her role includes providing primary health care for women in the western Idlib region.

(Writing by Tom Perry Editing by Alexandra Hudson)