chemical attack that killed at least 58 people including 11 children under the age of eight in Idlib province has been described as one of the worst attacks of the conflict in Syria. The Syrian Coalition, an opposition group based outside the country, said government planes carried out the air strike on the town of Khan Sheikhoun. It said the planes fired missiles carrying poisonous gases, describing the attack as a "horrifying massacre".
A Syrian military source denied allegations that government forces had used chemical weapons, dismissing the accounts as rebel propaganda. The army "has not and does not use them, not in the past and not in the future, because it does not have them in the first place", the source said.
4 April 2017: Syrian children receive treatment following a suspected toxic gas attack in Khan Sheikhun, a rebel-held town in the northwestern province of Idlib
4 April 2017: A civil defence member breathes through an oxygen mask, after what rescue workers described as a suspected gas attack in the town of Khan Sheikhoun in rebel-held Idlib
ceasefire that Turkey and Russia brokered in December, fighting has intensified in Syria over the past two weeks. Insurgent groups have launched wide offensives on parts of the capital Damascus, and the central province of Hama. Syrian and Russian air strikes have pounded rebel-held areas on the outskirts of the capital as well as various parts of Idlib. US air strikes have also hit several areas in the rural province where jihadists have a powerful presence.
The UN Special Envoy for Syria Staffan de Mistura said he is deeply concerned by the recent escalation of violence in Syria. Meanwhile, both Turkish President Tayyip Erdogan and Russian President Vladimir Putin have emphasised the importance of maintaining the ongoing ceasefire. However, with multiple infringements occurring every day, one has to wonder whether there is a ceasefire in place at all.
IBTimes UK looks back at some of the biggest attacks since the ceasefire came into effect at the beginning of the year.
12 January 2017: Smoke billows from a rebel-held area of Daraa in southern Syria, following reported shelling by pro-government forces
12 January 2017: Syrian civil defence volunteers carry a wounded man following a reported air strike by government forces in the Syrian town of Binnish, on the outskirts of Idlib
Omar haj Kadour/AFP
18 January 2017: Syrian Civil Defence volunteers, also knowns as the White Helmets, rescue children from a damaged building following a reported air strike that targeted the Idlib bus station
Omar haj Kadour/AFP
31 January 2017: The body of a Syrian infant lies in a morgue in the rebel-held town of Douma, on the outskirts of the capital Damascus, following reported shelling by government forces
7 February 2017: People inspect the damage at a site hit by air strikes in the rebel-held city of Idlib
19 February 2017: A member of the Syrian Arab Red Crescent runs as he searches for victims following a reported government air strike on the rebel-held town of Douma, on the eastern outskirts of the capital Damascus
20 February 2017: Fire and smoke billow following a reported car bomb explosion at a Syrian pro-government position during clashes between rebel fighters and regime forces to take control of an area in the southern city of Daraa
20 February 2017: A woman sits with injured children at a hospital following a reported strike by government forces in the rebel-held district of Barzah on the northeastern outskirts of Damascus
Saria Abu Zaid/AFP
21 February 2017: A fighter from Jaish al-Islam aims a Russian-made sniper rifle in the rebel-held area of Harasta, on the northeastern outskirts of the capital Damascus
22 February 2017: Smoke billows from buildings following reported air strikes on the southern Syrian city of Daraa
25 February 2017: A member of the Syrian civil defence, known as the White Helmets, reacts after an air strike during a rescue operation in the rebel-held town of Binnish, on the outskirts of Idlib
Omar haj Kadour/AFP
25 February 2017: A man carries a child from the rubble of destroyed buildings following a reported government air strike on the rebel-held town of Douma, on the eastern outskirts of the capital
15 March 2017: Smoke billows following reported air strikes by Syrian government forces on Damascus' north-eastern rebel-held al-Qaboun suburb
15 March 2017: Members of the Syrian civil defence, known as the White Helmets, remove a victim from the rubble of a destroyed building following a reported air strike in the northwestern city of Idlib
Omar haj Kadour/AFP
15 March 2017: Syrian security forces inspect the scene of a reported suicide bombing at the old palace of justice building in Damascus
19 March 2017: Civilians and a civil defence personnel carry children at a damaged site after an air strike on rebel-held Idlib
23 March 2017: Umm Mohammed and her husband drink coffee at their destroyed home in the rebel-held town of Douma, on the outskirts of Damascus
19 March 2017: An opposition fighter from the Failaq al-Rahman brigade fires a heavy machine gun in Jobar, a rebel-held district on the eastern outskirts of the Syrian capital Damascus
22 March 2017: Fighters run down a street, as plumes of smoke rise from a burning tyre, which is meant to disrupt warplanes in the Syrian town of Tayyibat al-Imam
Omar Haj Kadour/AFP
24 March 2017: Smoke rises from buildings following an air strike on Jobar, a rebel-held district on the eastern outskirts of the Syrian capital
24 March 2017: Syrian civil defence volunteers, known as the White Helmets, try to extinguish a fire reportedly caused by air strikes in the northwestern city of Idlib
Omar haj Kadour/AFP
25 March 2017: A Syrian man carries two injured children after a reported air strike in the rebel-controlled town of Hamouria, in the eastern Ghouta region
25 March 2017: The wrapped body of a Syrian child waiting to be transported is seen after an air strike in the rebel-controlled town of Hamouria, in the eastern Ghouta region on the outskirts of Damascus
27 March 2017: The body of Yousef, an eight-year-old boy who was killed by a reported air strike by Syrian government forces, is seen at a morgue in Douma, a rebel stronghold east of Damascus
1 April 2017: A Syrian forces' observer looks through a scope as smoke plumes rise on the horizon near the town of Qumhanah in the countryside of the central province of Hama
2 April 2017: A Syrian rebel fighter stands behind a window in a heavily damaged neighbourhood of Daraa, in southern Syria
3 April 2017: Man runs for cover amid the dust and smoke following a reported government air strike on the rebel-controlled town of Hamouria, in the eastern Ghouta region on the outskirts of Damascus
3 April 2017: A Syrian man pulls a body to be buried following reported air strikes by government forces in the rebel-held town of Douma, on the eastern outskirts of Damascus
4 April 2017: A child receives treatment following a suspected toxic gas attack in Khan Sheikhun, a rebel-held town in Idlib province
A joint investigation by the United Nations and the international chemical weapons watchdog determined the Syrian government was behind at least three attacks in 2014 and 2015 involving chlorine gas and Isis group was responsible for at least one involving mustard gas.
Damascus has repeatedly denied using such weapons during the six-year war, which has killed hundreds of thousands and created the world's worst refugee crisis. The Syrian conflict pits President Bashar al-Assad's government, helped by Russia and Iranian-backed militias, against a wide array of rebel groups, including some supported by Turkey, the United States and Gulf monarchies.