It is "highly probable" that Syrian government forces and their allies are responsible for a string of deadly attacks on health facilities in northwestern Syria, according to a summary of an internal United Nations inquiry.

The summary, a copy of which Al Jazeera has seen, said it was "highly probable" that the government of President Bashar al-Assad or its allies were behind three of seven attacks investigated by the board.

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The world governing body said it was "plausible" that the Syrian government or its allies carried out one attack while pointing to the existence of one case where it was "highly probable" that government forces acted alone.

"When they say its allies, which is what it mentioned in the report, we know that there is only one that the Syrian government with air power and that is Russia," said Al Jazeera's James Bays, reporting from the UN headquarters in New York.

The inquiry also found it "probable" that a deadly attack on a Palestinian refugee camp in Syria's Aleppo was carried out either by armed opposition groups or by the Hay'et Tahrir al-Sham (HTS) alliance, formerly known as al-Nusra Front.

It said the belligerents were provided with the coordinates of the facilities.

The summary, prepared by UN Secretary-General Antonio Guterres on the basis of a 185-page confidential internal report, was submitted to the UN Security Council's 15 members.

The UN investigation focused on seven air raids, including one that was dropped from the report's conclusions because the UN had not relayed the coordinates of that site to the belligerents, Guterres said in a letter accompanying the summary.

"The impact of the hostilities on civilian and humanitarian sites in northwest Syria is a clear reminder of the importance for all parties to the conflict to observe and ensure respect for international humanitarian law," Guterres said. "According to numerous reports, the parties have failed to do this".

The UN chief attributed the small number of incidents examined to the absence of UN personnel on the ground, which made it difficult to determine what had happened.

At the end of July 2019, 10 Security Council members issued a rare demarche - a formal diplomatic petition - demanding that Guterres open an investigation into air attacks on medical installations, infuriating Russia.

The 10 were: Germany, France, Belgium, the UK, the United States, Indonesia, Kuwait, Peru, Poland and the Dominican Republic.

The board of inquiry was established in September and began working September 30.

Its report was supposed to have been submitted by the end of 2019, but was delayed until March 9.

Western countries for months have demanded that a summary of the report be published, but that, too, was delayed until now.

"Though the report is inconclusive, it remains pretty damning for the Syrian government," said Bays.

"They reveal that they weren't given visas, they weren't given any help at all, it didn't respond to the inquiries that the board made during its several months of work."

In his letter, Guterres stressed that the board of inquiry was not a criminal investigation and that its aim was to improve UN procedures and prevent attacks of this kind in the future.

Fighting has calmed in the northwestern region after Turkey, which backs rebels opposed to al-Assad and ramped up its deployment earlier this year, agreed on a ceasefire with Russia a month ago. The fighting has displaced nearly 1 million people in Idlib since December.