Syrian government forces carried out three chemical attacks on a rebel-held village in 2017, according to a new investigation by the OPCW. Based on the available evidence, that is the only conclusion that can "reasonably be reached", it said in a 82-page report published on Wednesday:

"At approximately 6:00 on 24 March 2017, an Su-22 military airplane belonging to the 50th Brigade of the 22nd Air Division of the Syrian Arab Air Force, departing from Shayrat airbase, dropped an M4000 aerial bomb containing sarin in southern Ltamenah, affecting at least 16 persons.

"At approximately 15:00 on 25 March 2017, a helicopter of the Syrian Arab Air Force, departing from Hama airbase, dropped a cylinder on the Ltamenah hospital; the cylinder broke into the hospital through its roof, ruptured, and released chlorine, affecting at least 30 persons.

"At approximately 6:00 on 30 March 2017, an Su-22 military airplane belonging to the 50th Brigade of the 22nd Air Division of the Syrian Arab Air Force, departing from Shayrat airbase, dropped an M4000 aerial bomb containing sarin in southern Ltamenah, affecting at least 60 persons."

This is the first report by the OPCW's Investigation and Identification Team (IIT) which is tasked with identifying those responsible for chemical attacks in Syria.

The three attacks on Ltamenah, a village in Hama province, were previously investigated by the organisation's Fact-Finding Mission, but its role was only to establish whether chemical weapons were used, not to attribute blame.

The mandate of the IIT goes much further and its report focuses on three aspects that point to the likely culprit – the type of munitions used, the chemicals they contained and the means of delivery.

The report leaves little room for doubt as to who was responsible. The munitions were of a type possessed by the regime, it says, and were dropped by the Syrian air force. In the case of the two munitions containing the nerve agent sarin, chemical markers indicate that the sarin was produced according to the formula used by the regime.

These attacks, it should be noted, occurred after the regime had formally renounced chemical weapons and supposedly declared all its stockpiles to the OPCW for destruction.

The report also pre-emptively addresses some of the criticisms that are likely to come from Syria, Russia, and the regime's defenders on social media.

The IIT was established in the face of opposition from Syria and its allies after Russia used its Security Council veto to shut down a previous UN/OPCW body known as the Joint Investigative Mechanism (JIM) which also had a mandate to determine culpability. Syria and Russia accused the JIM of bias after it issued a report blaming the regime for a sarin attack on Khan Sheikhoun in 2017.

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Yesterday's report makes clear that the IIT gave the regime plenty of opportunities to state its case – but received no response. It says the IIT decided not to draw any inference from this lack of cooperation and remains willing to "consider any information that the Syrian Arab Republic may wish to share".

The report also says the IIT considered various scenarios, including the idea promoted by the regime and its defenders that the attacks were false flag operations "staged" by rebels.

Among the report's appendices is a letter to the Syrian authorities asking for more details about claims they had made regarding rebels faking videos of attacks and training civilians "to pretend to suffer symptoms of exposure to chemicals".

In connection with such claims, the report says the IIT "did not receive, nor was otherwise able to obtain, any material that would substantiate them. It nonetheless took these hypotheses into account when scrutinising other information."

The report looks in some detail at one such hypothesis – that armed groups had retrieved fragments of sarin munitions from the regime's testing range for the purpose of faking attacks – and explains why it is implausible. Among other things, the report points out that there were no fragments of sarin munitions to be found on the range, because the chemical munitions tested there had contained sulfur mustard.