Attack killing three White Helmets comes days after more than 60 people were killed by a suspected Russian and Syrian airstrike
Three Syrian Civil Defence rescue volunteers were killed in the Damascus area of Eastern Ghouta by a suspected Syrian government air strike on Friday.
Mohammed Alaya, Mohammed Haymour and Ahmed Keika were killed inside their base in Douma, a neighbourhood in Eastern Ghouta, the rescue group said in a statement on Saturday.
The deaths come after reports on Friday that shelling by the Syrian government on the rebel-held areas of Eastern Ghouta killed at least 19 civilians, among them six children, a monitor said.
The area, which has been besieged since 2013, has faced a series of air strikes from Russian and Syrian government warplanes in the past few months despite the area being designated a de-escalation zone.
The de-escalation zones were created following a deal between Iran, Russia and Turkey in a bid to establish a ceasefire between Syrian's government and opposition rebels in areas across Syria.
The killing of the rescue volunteers also comes after more than 60 people were killed this week in a market in Atareb, in Aleppo province.
The Syrian Civil Defence condemned the killing of its volunteers and accused forces loyal to President Bashar al Assad of purposely "targeting civilian centres and aid workers".
We lost another 3 heroes of #TheWhiteHelmets.
"Mohammed Alaya, Mohamed Haymour and Ahmad Kaeika" Volunteers of @SyriaCivilDef in #EasternGhouta, killed by #Assad warplanes during their humanitarian duty in #Douma city. pic.twitter.com/RH8dcVsFbm
— SCD Rif-Dimashq (@SCDrifdimashq) November 17, 2017
The rescue group also called on the United Nations to "take urgent action" to stop the bombing of Eastern Ghouta.
"Today the regime air force targeted Syrian Civil defence team while they were working in Douma City. Three volunteers were killed and most of the other volunteers were injured," the statement said.
"We in the Syrian Civil Defence condemn this barbaric bombardment and call on the United Nations and the guarantors of the de-escalation agreements to take urgent action to stop all kind of targeting."
On Saturday, medical staff in Ghouta underlined concern that another chemical attack has taken place in the area.
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According to Mohamad Katoub, an advocacy manager for the Syrian American Medical Society, said that his organisation had found "symptoms indicative of phosphorus compounds".
Eastern Ghouta has been subject to numerous chemical attacks and has taken the brunt of a crippling siege by the Syrian government for more than four years.
The Syrian government is now in the midst of a large-scale offensive in East Ghouta, the Washington, DC-based Syria Institute told MEE on Friday.
In the past four days, the government has unleashed 222 air strikes – including cluster bombs and chlorine attacks - in the area, with half of them in Harasta, said Valerie Szybala, the executive director of the Syria Institute.
In retaliation for the latest Ghouta shelling, rebels fired rockets into Damascus on Friday, killing three civilians, a source told AFP.
Six were killed the previous day, including Syria's national karate coach Fadel Radi, who died of his wounds after being hit by shrapnel as he left his Damascus sports club, the state-run SANA news agency reported.
Around 400,000 people have lived under air and artillery attacks, the blocking of food and medical aid, the blocking of medical evacuations, as well as an end to free movement and the blocking of all normal commercial traffic.
More than 330,000 people are estimated to have been killed and millions displaced in the Syrian war, which began in 2011.