Death Toll From Suspected US Raid in Syria Grows Amid Medical Crisis, Say Activists

U.S. says it's investigating reports that scores were killed in airstrikes.

— London -- The civilian death toll from suspected U.S.-led airstrikes in northern Syria earlier this week is rising sharply because of a lack of medical facilities to care for those wounded near the besieged city of Manbij, activists warn.

"The number is increasing because of the lack of hospitals or clinics," Houran told ABC News. "Most of the wounded civilians are dying because of the siege."

He said that civilians in the area had relocated to the northern part of al-Tukhar to seek shelter from airstrikes, where some 200,000 civilians are believed to be living under siege. Members of one family were afraid to stay in their home and were sleeping in a vehicle when they were killed in the airstrikes, he said.

ABC News has received photos purportedly from al-Tukhar taken by local activists after the airstrikes. Several show dead bodies of young children -- some appear to be toddlers.

"One concern is that usually one would expect that a party to a conflict would be able to improve its civilian casualty, but it looks like the U.S.-led coalition is worsening, particularly in the Manbij area," Neil Sammonds, Amnesty International's lead researcher on Syria, told ABC News. "That's not acceptable. We have laws of war, and the U.S., like everyone else, must do all it can to abide by those laws. They must take all precautions to check if civilians are there and should not use weaponry which is likely to cause damage to areas where more civilians are likely to be killed. They should more closely check information that they are given about presence of civilians and not just assume that if they can't see civilians in a picture from the sky, there are no civilians there."

Amnesty International looked into 11 U.S.-led airstrikes over the last two years and found that they resulted in the killing of 250 to 300 civilians, but the U.S. recognized only five civilian deaths in those incidents, he said. In the past two years, at least 700 civilians have been killed by U.S.-led airstrikes, according to Sammonds, who said that the U.S. recognized only 24 civilian deaths by U.S.-led airstrikes for the same period.

In a statement to ABC News, U.S. Central Command said that it will investigate the reports of civilian deaths.