The symptoms, he said, included unconsciousness, foaming from the nose and mouth, constricted pupils, fast heartbeat and difficulty breathing. People died of asphyxiation, he said.
"The inspectors will not come," said a resident who didn't want his name used. "If they wanted to come, they would have come a long time ago.
"The Assad regime determines where the inspectors go, and they will not let them go there. There is already a siege around eastern Ghouta from the Assad regime."
'Held to account'
Rights group Human Rights Watch also called Wednesday for the U.N. inspection team to be given immediate access to the area.
"Whether or not chemical weapons were used, the attack left a large number of civilians dead, and those responsible for unlawful killings should be held to account," it said.
U.N. children's agency UNICEF said the reports of Wednesday's attack on civilians were deeply disturbing and that those who failed to protect children must be held accountable.
Syria's official news agency, SANA, quoted Iranian Foreign Minister Mohammad Javad Zarif on Thursday as saying the rebels must be behind any chemical weapons attack, if confirmed, as "they do not hesitate to commit any crime."
Russian officials, meanwhile, dismissed the claims of chemical weapons as a "provocation planned in advance," Russian Foreign Ministry spokesman Alexander Lukashevich told Interfax news agency. He suggested it was timed to coincide with the visit by the U.N. team.