ISTANBUL -- President Trump and Ambassador Nikki Haley have condemned an apparent chemical attack against civilians in Syria by the Assad regime and the U.S. is considering a possible response.

According to medics, survivors in the town of Douma outside the Syrian capital of Damascus smelled strongly of chlorine, a chemical that can be deadly in confined spaces and especially toxic for children.

CBS News cannot independently verify videos out of the city, but many of the dead seem to have collapsed, with no obvious signs of injury. We spoke with one medic by phone who told us he treated around 70 of the victims, but for his own safety, asked that we not identify him.

This image made from video released by the Syrian Civil Defense White Helmets, which has been authenticated based on its contents and other AP reporting, shows a medical worker giving toddlers oxygen through respirators following an alleged poison gas attack in the opposition-held town of Douma, in eastern Ghouta, near Damascus, Syria, Sunday, April 8, 2018. Syrian Civil Defense White Helmets / AP

"Everyone who had a cough, a bloody cough, after that died," he said. "One of them was my patient, about 55. I tried to save him."

The Syrian regime is accused of using chlorine as a weapon many times before, and this alleged chemical bombardment comes as the regime attacks the rebel stronghold of eastern Ghouta. But the regime, as always, denies it's used chemical weapons. Its ally Russia was even more categorical, and called the allegations "fake news."

Overnight, airstrikes targeted a Syrian regime airbase near the city of Homs, and according to Russia they were fired by two Israeli fighter jets. The airbase is used by the regime's other backer, Iran.

It's unclear if the strikes were connected with the alleged chemical attack, but the carnage of the last 48 hours lays bare the proxy war being fought in Syria. Iran and Russia back the regime, regardless of its atrocities, and now the U.S. must again decide how to respond.

A year ago, the U.S. responded to a sarin nerve agent attack in Syria by launching nearly 60 cruise missiles targeting a Syrian regime airbase. On Monday, Russia threatened "grave repercussions" if the U.S. takes military action again.