Two people died after the attacks in Syria's Hama province at the end of March 2017. Dozens of people suffered severe respiratory symptoms.
The banned nerve agents sarin and chlorine were used in attacks in northern Syria last year, the global chemical weapons watchdog said on Wednesday.
It is the latest in a series of reports from the Organisation for the Prohibition of Chemical Weapons (OPCW) confirming the use of toxic agents in the country’s civil war.
The OPCW is also investigating a suspected chemical attack on April 7, this year in the Douma enclave near Damascus, which prompted missile strikes by the United States, France and Britain.
It is expected to publish the results of that inquiry this month.
The OPCW said in a statement that sarin had been used south of the city of Ltamenah in the Hama area on March 24, 2017.
It also “concluded that chlorine was very likely used as a chemical weapon at Ltamenah Hospital and the surrounding area on 25 March 2017”.
TRT World's Oubai Shahbandar has more details from the southeastern Turkish city of Cizre, on the Syrian border.
The findings in Ltamenah were based on witness testimony, epidemiological analysis and environmental samples, it said.
The OPCW did not assign blame for the attack. The Syrian regime denies using chemical weapons.
Syrian regime forces have used both sarin and chlorine, according to a United Nations-OPCW joint investigation, while rebel forces used sulphur mustard gas once.
Their so-called JIM mission was disbanded in November after a proposed renewal of its mandate was vetoed by Russia on the UN Security Council.