A Russian-built plane used by the Syrian air force conducted a sarin gas attack in the spring that killed at least 83 civilians and sparked a retaliatory US strike, a UN investigation has found.
The latest report by the Commission of Inquiry on Syria also said US forces failed to take "all feasible precautions" to protect civilians in attacking alleged terrorists in Aleppo in March, destroying part of a mosque complex.
The report offers some of the strongest evidence yet of allegations that President Bashar Assad's forces conducted the April 4 attack on Khan Sheikhoun in rebel-held Idlib province.
The US quickly launched a punitive strike on Shayrat air base, where the report says the Sukhoi-22 plane took off.
The report issued on Wednesday covers a period from March to early July.