BEIRUT/moscow - A Syrian rescue service operating in rebel-held territory said on Tuesday a helicopter dropped containers of toxic gas overnight on a town close to where a Russian military helicopter was shot down hours earlier.

A spokesman for Syria Civil Defence said 33 people, mostly women and children, were affected by the gas in Saraqeb, in rebel-held Idlib province. The group, which describes itself as a neutral band of search and rescue volunteers, posted a video on YouTube apparently showing a number of men struggling to breathe and being given oxygen masks by people in civil defence uniforms.

Syria Civil Defence workers, who went to the scene of the attack, said they suspected the gas was chlorine but could not verify that. “Medium-sized barrels fell containing toxic gasses. The Syrian Civil Defence was not able to determine the type of the gas,” said the spokesman. The Syrian government and its Russian allies were not immediately available for comment.

The Civil Defence spokesman said it was the second time Saraqeb had been hit by toxic gas. The group was aware of around nine suspected chlorine gas incidents across Idlib province since the conflict began, he said.

Monitors at the Britain-based Syrian Observatory for Human Rights, which tracks violence on all sides in the civil war, said barrel bombs fell on Saraqeb late on Monday, wounding a large number of citizens.

Russia’s defence ministry said a Russian helicopter was shot down near Saraqeb during the day on Monday, killing all five people on board, in the biggest officially acknowledged loss of life for Russian forces since they started operations in Syria. The helicopter came down in Idlib province, roughly mid-way between Aleppo and Russia’s main air base at Khmeimim in the western province of Latakia, near the Mediterranean coast.

Russian air power began supporting Syrian President Bashar al Assad late last year, an intervention which tipped the balance of the war in Assad’s favour, eroding gains the rebels had made that year.

The Russian defence ministry said the Mi-8 military transport helicopter was shot down after delivering humanitarian aid to Aleppo as it made its way back to Khmeimim. No group has claimed responsibility for downing the helicopter.

Government and opposition forces have both denied using chemical weapons during the five-year-old civil war. Western powers say the government has been responsible for chlorine and other chemical attacks. The government and Russia have accused rebels of using poison gas.

Meanwhile, Moscow on Tuesday blasted criticism by Washington over its actions in Syria, saying it was "unacceptable" to demand restraint around Aleppo, the city divided between Syrian government troops and rebels.

"As soon as there is real headway in fighting terrorists, made by the Syrian government and army with our support, the Americans started... demanding that we stop fighting terrorists," Deputy Foreign Minister Sergei Ryabkov told RIA-Novosti agency.

Britain-based monitors reported that Russia launched heavy air strikes in the Aleppo outskirts, slowing a last-ditch effort by rebels to break the siege.

US Secretary of State John Kerry on Monday called on Russia and its Damascus ally to restrain "from conducting offensive operations" in Aleppo, where regime forces surrounded rebel-held districts.

Kerry said the attacks prevented the warring parties from meeting Monday, the target date set for the regime and opposition to agree on the framework for political transition.

"We will see in the course of the next hours, few days, whether or not that dynamic can be changed," Kerry said.

Ryabkov however rejected such talk as an ultimatum.

"To hear from Washington that... the next hours and days will be decisive, that is an ultimatum-like, unacceptable tone. I think this is regular blackmail that is common to the Americans," said Ryabkov.

Moscow had announced the launch of humanitarian corridors out of Aleppo for civilians and surrendering rebels, a scheme that some NGOs said was "deeply flawed," calling instead for a UN-mandated plan of escape routes.

Ryabkov countered that the US itself uses the corridor scheme and is only against it because Syrian President Bashar al-Assad's forces are crushing opponents who have not joined the ceasefire or surrendered.

"Why can it not be done with Aleppo? Because in Syria the Syrian government has finally begun to separate terrorists from the moderate (opposition) and civilians. That is what our colleagues in Washington were not ready to do" for months, he said.



UN investigators established that sarin gas was used in Eastern Ghouta in 2013. The United States accused Damascus of that attack, which it estimates killed 1,429 people, including at least 426 children. Damascus denied responsibility, and blamed rebels.

Later that year the United Nations and the Syrian government agreed to destroy the state’s declared stockpile of chemical weapons, a process completed in January 2016.

The Organisation for the Prohibition of Chemical Weapons confirmed in late 2015 that sulphur mustard, commonly known as mustard gas, had been used for the first time in the conflict, without saying which party in the many sided conflict it thought had used it.

Meanwhile, US Secretary of State John Kerry has urged Russia to “restrain” itself and the government in Syria as fierce fighting there continues on the day he had hoped political transition could start.

“It is critical, obviously, that Russia restrain both itself and the Assad regime from conducting offensive operations, just as it is our responsibility to get the opposition to refrain from engaging in those operations,” he told journalists.

Kerry said the government’s attacks had prevented the warring parties from meeting for negotiations on Monday, the target date set for the regime and opposition forces to agree on the framework of a political transition.

“The target date was set with the agreement that the parties were going to be able to go to the talks and begin immediately to negotiate,” he said.

“But because of the continued offensive operations of the Assad regime, the opposition found it impossible to sit in Geneva and actually negotiate without the cessation of hostilities.”

President Bashar al-Assad’s forces have surrounded rebel-held districts in the city of Aleppo, one of the main front lines in the conflict ravaging the country since 2011.

Aleppo’s southern edges have been ravaged by intense fighting in recent days as rebels seek to ease the government siege and cut off the regime’s own access route into the rest of the northern province.

Russia and the United States are nominally co-chairs of an international effort to bring Assad’s regime to the negotiating table with armed opposition groups.

Hopes for the existing peace process rest on a UN-backed blueprint sketched out by the 22-country International Syria Support Group.

Under the roadmap, signed by both Syria’s ally Iran and Assad’s pro-rebel foe Saudi Arabia, a nationwide ceasefire would precede Geneva-based talks on “political transition.”

The plan, endorsed by the UN in December, calls for the creation of a transitional body that should have taken place on August 1, followed by a new constitution and elections by mid-2017.

“Almost all of the time, from the moment of the announcement of the target date until today, has been consumed by trying to get a cessation of hostilities in place that is meaningful,” Kerry said, implicitly acknowledging the failure to meet the roadmap so far.

“These are important days to determine whether or not Russia and the Assad regime are going to live up to the UN, live up to the cycle, or not,” Kerry said. “And the evidence thus far is very, very troubling to everybody.”

“We will see in the course of the next hours, few days, whether or not that dynamic can be changed.”