Assad regime accused of 35 chlorine attacks since mid-March

"One of the children died in silence before we got to the hospital,” said Raed Saleh, the head of a Syrian civil defence force called the White Helmets. "We did what we could to save her, but dying in silence was her fate. Death in silence before the whole world.”

Saleh said it was the second chemical attack that night, an opening salvo in a campaign in which three-dozen such barrel bombs were dropped, according to medical and humanitarian workers, mostly on civilian targets in Idlib province, which fell to a coalition of rebel fighters in March.

Muhammad Tennari, the manager of Sarmin hospital, was there on that first night, and since then has treated the near-daily stream of victims with symptoms of chlorine exposure.

"The children who came to us were suffocating and we couldn’t do anything because they had breathed too much chlorine,” Tennari told the Guardian from Idlib, describing the most difficult cases he had to handle. "It’s very distressing to see children suffocating in front of you and you cannot do anything.”

Syrian civil defence workers and doctors have documented 35 barrel bomb attacks where chlorine was allegedly used since 16 March – the latest of which was on Tuesday near the former regime stronghold of Jisr al-Shughour – with more than 1,000 injuries and nine deaths. More than 20 civil defence workers have been wounded in rescue operations.

"Whenever the regime loses an area or a city it arbitrarily takes revenge on civilians,” said Saleh. "It is targeting civilians.”

Tennari said most of the victims came in without physical wounds, but had acute respiratory problems and burning, bloodshot eyes. Videos show medics pouring water on the victims after removing their clothes to reduce their skin’s exposure to the chemicals, before giving them oxygen masks and respiratory medication.

"Most of the targeting is of civilian areas, and most of the injured are women and children,” Tennari said. "It’s almost daily now.”

The vast majority of the attacks occurred in towns and villages in Idlib, and civil defence workers say they have run out of medicine to treat the symptoms of chlorine attacks.

The northern province has suffered from a punishing air campaign by Bashar al-Assad’s regime after most of it fell to rebels backed by Saudi Arabia and Turkey in late March. The rebels, known as Jaish al-Fatah, include conservative Islamists, mainstream Free Syrian Army battalions, and Jabhat al-Nusra, the al-Qaida affiliate in Syria.