GAZIANTEP, TURKEY // Blood samples from Syrians who died of unknown causes after rocket attacks have been smuggled to Jordan to be tested for chemical weapons.
While investigations into possible chemical warfare continue, the doctor and other activists in Damascus have warned that panic in the city over the issue is hindering humanitarian and medical relief efforts.
Both the regime and rebels have accused each other of using chemical agents, but no indisputable evidence has been made public.
An Israeli intelligence official said on Tuesday that Israel believed Bashar Al Assad's military had used chemical weapons, possibly sarin, a deadly nerve agent. France and Britain have also said they have evidence.
The White House said US agencies had not been able to prove such weapons had been deployed, and urged caution. But at a Nato meeting in Brussels this week, John Kerry, the US secretary of state, said the organisation needed to plan its response to a possible chemical attack.
Efforts inside Syria to document chemical weapons use continue. A doctor in charge of field hospitals in Damascus and the surrounding countryside said his team had collected blood samples from people who died after exposure to what may have been a chemical attack.
"Our assessment is that it may have been chemicals that killed them but I don't have the technical facilities to test that so we have smuggled samples out to European embassies in Jordan for examination," the doctor said. "They should have the expertise to do those tests."
The doctor said his staff had reported three separate incidents over the past five months in which they believed chemical weapons might have been used in Damascus and the densely populated surrounding suburbs - in Taibeh, Daraya and Adra.
After rocket strikes in those areas, 15 injured people were taken to hospital, and four of them died, without showing any wounds from shrapnel or explosives, he said.
Later examination of the areas where the rockets had landed showed cats, dogs and goats had died - also without visible wounds.
"Patients were brought in and they had lost consciousness, some were having spasms, they had dilated pupils which would be clinical symptoms of chemical agents," the doctor said. He stressed that, in the absence of rigorous laboratory testing, it was impossible to say what had killed the victims.
The field hospitals had not been able to provide much help.
"We have no experience in how to treat this kind of thing and we don't have the drugs, we've got some atropine which is a pretty standard antidote to poisonings but that's really all we can do," he said.
The doctor said there was growing fear of chemical weapons among civilians in and around the capital.
"We're trying to give people advice so they don't feel helpless, we've handed out leaflets telling them what to do if there is an attack - stay indoors, shut the windows, that kind of thing," he said.
"In reality, there's not much we can do about it."
Activists inside Syria have become frustrated that panic over chemical weapons has diverted attention and resources from more mundane yet pervasive problems.
As rudimentary field hospitals in rebel-held areas struggle to obtain basic medical supplies, there have been disagreements over how best to allocate limited supplies given a possible chemical threat.
"There are people who are seriously advocating that we stockpile military-grade gas masks so that we can protect everyone if there is a chemical attack," said an activist in Damascus involved in medical relief efforts.
He dismissed the plan as absurd, and said it would not work and would merely waste money and effort.
"We still don't have enough basic medicines and surgical equipment to treat the wounded we get every day, and there are people without enough food to eat, we should focus on these things, not chemical weapons, which we'll be helpless against anyway if they are used," he said.
At recent meetings of opposition figures in Damascus, the question of buying and smuggling in gas masks had been brought up repeatedly, said the activist.
Some activists said there was little prospect of getting the masks past a ring of security checkpoints into the city, let alone distributed and people properly trained in their use.
Unless gas masks are correctly fitted, equipped with the right filters and put on immediately in the event of a chemical attack, they offer no real protection.
They are also ineffective against some chemical agents, including sarin, which can be absorbed through the skin. To safeguard against that, a full protective chemical warfare suit is required.
"It's distracting us, I understand why people are talking about it, but it's not the best thing we could be doing," the activist said.
"I'm still not sure if chemicals have been used, but when it gets talked about in the media, the opposition committees start talking about it too, it takes over everything else."
Brig General Itai Brun, who heads the military intelligence research unit at the Israeli Defence Forces, said the Syrian regime had used chemical weapons.
"To the best of our professional understanding, the regime has made use of deadly chemical weapons against the rebels in a number of incidents in the past few months," he said.
He said photographs showed victims of suspected attacks foaming at the mouth and with contracted pupils, indications that sarin gas might have been used.
The claim added to pressure on the US and the international community to respond. Washington has said use of chemical weapons would represent a red line.
Mr Kerry subsequently said he had discussed the issue with the Israeli prime minister, Benjamin Netanyahu, and that there had been no confirmation of chemical weapons use.
"We support an investigation, we're monitoring this, and we have not come to the conclusion that there has been that use," said White House spokesman Jay Carney.
A UN team of experts formed to investigate the alleged use of chemical weapons has been unable to enter Syria, amid a dispute over its access.
The UN wants to investigate a list of sites, something the authorities in Damascus have refused, underlining the huge political implications were chemical weapons to have been used.