All available evidence strongly suggests that on April 4, 2017, a Syrian government warplane attacked Khan Sheikhoun, a town in the northwestern governorate of Idlib, with a nerve agent, killing at least 92 people, 30 of them children. The death toll likely makes this the deadliest chemical attack since an attack killed hundreds in Ghouta, near Damascus, in August 2013.
The Khan Sheikhoun attack sparked international outrage, but the attack on Khan Sheikhoun was not the only recent chemical attack by the Syrian government. Three developments since late 2016 show that the Syrian government’s use of chemical weapons has become widespread and systematic:
Government warplanes appear to have dropped bombs with nerve agents on at least four occasions since December 12, including in Khan Sheikhoun;
The government’s use of helicopter-dropped chlorine-filled munitions has become more systematic;
Government or pro-government ground-forces have started using improvised ground-launched munitions containing chlorine.
In at least some of the attacks, the intention appears to have been to inflict severe suffering on the civilian population, which would amount to crimes against humanity.
After the chemical attacks in Ghouta, the United Nations Security Council demanded that the Syrian government destroy its chemical stockpiles, weapons, and production capacity. In response, Syria acceded to the Chemical Weapons Convention in September 2013. In June 2014, the Organisation for the Prohibition of Chemical Weapons (OPCW) announced that it had shipped Syria’s declared chemical weapons out of the country for destruction, though it continued attempting to verify the accuracy and completeness of the Syrian declaration.
But in fact, the Syrian government had already been using helicopters to drop improvised munitions filled with chlorine at least since April of that year. While the Chemical Weapons Convention does not ban chlorine because it has many civilian uses, the convention bans its use as a weapon. Yet, between April 2014 and late 2016, Human Rights Watch documented 16 Syrian government attacks with chlorine contained in improvised air-dropped munitions. The number of attacks reported in the media and on social media is much higher. A UN-OPCW Joint Investigative Mechanism found enough evidence in three attacks with chlorine in 2014 and 2015 to conclude that the government was responsible.
Human Rights Watch interviewed 60 people with first-hand knowledge of the chemical attacks and their immediate aftermath, and reviewed dozens of photos and videos of impact sites and victims that were posted online and provided directly by local residents, but was unable to conduct ground investigations of the attack sites.
Information from local residents in Khan Sheikhoun indicates that a warplane flew over the town twice around 6:45 a.m. on April 4, 2017. One resident said he saw the plane drop a bomb near the town’s central bakery in the northern neighborhood during the first fly-over. Several people, including the person who saw the bomb falling, said they heard no explosion but saw smoke and dust rising from the area, consistent with the relatively small explosive charge in a chemical bomb. Several people also confirmed that they saw people injured or heard reports of injuries immediately after the first fly-over. A few minutes later, they said, a warplane dropped three or four high-explosive bombs on the town.
Human Rights Watch identified 92 people, including 30 children, whom local residents and activists said died due to chemical exposure from this attack. Medical personnel said the attack injured hundreds more.
Human Rights Watch reviewed dozens of photos and videos provided by residents of a crater from the impact of the first bomb. Local residents believed this site was the source of the chemical exposure because those who died lived nearby and people who came near it, including first responders, exhibited the strongest symptoms of chemical exposure. One of the first photos of the crater, taken by first responders, shows what appears to be liquid on the asphalt. That would be consistent with the use of a bomb containing sarin, which is in liquid form at room temperature.
The photos and videos of the crater show two remnants from the chemical weapon used: a twisted thin metal fragment with green paint and a smaller circular metal object. Green coloring is widely used on factory-produced weapons to signify that they are chemical weapons. The KhAB-250, for example, one of two Soviet-produced bombs specifically designed to deploy sarin from a warplane, has two green bands. The circular object seen in photos of the crater appears similar to the cap covering the filling hole on the KhAB-250.
These remnants, combined with witness observations, the victims’ symptoms, and the identification of sarin as the chemical used in the attack by the French and Turkish governments and the Organisation for the Prohibition of Chemical Weapons, suggest that the Syrian warplane dropped a factory-made sarin bomb. According to open source material, the only Soviet-produced bombs designed specifically to deliver sarin are the KhAB-250 bomb, and its bigger version, the KhAB-500.
Evidence suggests that the Khan Sheikhoun attack is not the first time government warplanes have dropped nerve agents in recent months. Witnesses described to Human Rights Watch symptoms consistent with exposure to nerve agents that they and other local residents experienced after warplanes attacked eastern Hama on December 11 and 12 and northern Hama, near Khan Sheikhoun, on March 30, 2017.
The December attacks were in territory controlled by the Islamic State (also known as ISIS), which closely monitors communication, so it has been difficult to reach witnesses. But four witnesses interviewed by phone and two medical personnel interviewed via text message through intermediaries gave consistent accounts of the attacks. An opposition-affiliated activist and local residents provided the names of 64 people who died from chemical exposure in the December attacks.
The suspected nerve agent attack in northern Hama on March 30 caused no deaths, but injured dozens of people, both civilians and combatants, according to local residents, medical personnel, and first responders.
All four suspected nerve agent attacks were in areas where offensives by armed forces fighting the government threatened government military air bases.
Government forces’ use of chlorine-filled weapons has become more widespread and systematic. During the last month of the battle for Aleppo city, which ended on December 15, 2016, helicopters dropped multiple improvised chlorine-filled munitions in a pattern showing that the attacks were part of the overall military strategy to retake the city. Such attacks have continued more recently, for example, in al-Lataminah in northern Hama.
Since January 2017, Human Rights Watch has also documented, for the first time since August 2013, the use by government or pro-government ground forces of improvised surface-fired rockets containing chlorine to attack territory near Damascus controlled by armed groups fighting the government.
Some of the chemical attacks hit residential areas far from the frontlines without any obvious military target and appear to have killed and injured only civilians, suggesting the Syrian government forces directed at least some of the attacks against the civilian population.
The Syrian government has repeatedly denied using chemical weapons, including in Khan Sheikhoun on April 4. While Russia has carried out aerial attacks in the areas where chemical attacks took place, Human Rights Watch has no information to indicate that Russian authorities have used chemical weapons. However, Russian forces continue to provide active military support to Syrian forces despite extensive evidence that the latter are using chemical weapons and targeting civilians.
The Chemical Weapons Convention, which entered into force in 1997, prohibits the development, production, stockpiling, and use of chemical weapons, and requires their destruction. The prohibitions also apply to toxic chemicals with civilian uses, such as chlorine, when they are used as weapons. Syria became a party to the convention in October 2013.
Crimes against humanity consist of specific criminal acts committed on a widespread or systematic basis as part of an “attack on a civilian population,” meaning there is some degree of planning or policy to commit the crime. Such acts include murder and “other inhumane acts of a similar character intentionally causing great suffering or serious injury to body or to mental or physical health.” The prohibition of crimes against humanity is among the most fundamental in international criminal law and can be the basis for individual criminal liability in international courts, as well as in some foreign domestic courts under the principle of universal jurisdiction.
Human Rights Watch calls on the UN Security Council to immediately adopt a resolution calling on all parties to the Syrian conflict to fully cooperate with OPCW investigators and facilitate their unimpeded access to locations of chemical attacks, as required by UN Security Council resolutions 2118 and 2235. In line with the Security Council’s pledges to impose measures under Chapter VII of the UN charter in the event of continued chemical weapons use in Syria, Human Rights Watch also calls on the Security Council to adopt sanctions against those responsible for chemical attacks that UN-appointed investigations have confirmed. Human Rights Watch also urges UN member states to support the Syria accountability mechanism established by the UN General Assembly in December 2016, including by providing funds.