An internal UN inquiry determined that it is "highly probable" the Syrian regime and its allies carried out five of six investigated attacks in northwestern Syria that targeted civilian facilities, Secretary-General Antonio Guterres announced Monday.

The board determined that the attacks on a school, a hospital, two health care centers, and a child care center were most likely carried out by the regime or its allies, according to a summary of the inquiry's extensive report released by Guterres.

The investigators said it is "plausible" that an attack on a second health center was also carried out by the Assad regime or its allies.

Turning to a sixth incident, they said it is "probable" that an attack on a Palestinian refugee camp in Aleppo was conducted either by armed Syrian opposition groups or by Hayat Tahrir al-Sham, the strongest militant group in northwest Idlib that is affiliated with al-Qaida.

A summary of the 185-page confidential report by a board of inquiry appointed by U.N. Secretary-General Antonio Guterres was released Monday. It was formed to investigate incidents in Syria's northwest after Russia and Turkey agreed to establish a "de-escalation zone" in Idlib on Sept. 17, 2018.

Guterres said in a letter accompanying the report that the regime did not respond to repeated requests to visit the country.

Noting the findings, he said, "I would emphasize in this connection that a board of inquiry is not a judicial body or court of law: It does not make legal findings or consider questions of legal liability or legal responsibility."

When Guterres announced the board’s three members in September, he said he was initiating the investigation after claims, especially from human rights and humanitarian groups, that civilian facilities were being targeted despite their coordinates being given to the Syrian military and Russia a close ally of the Bashar Assad regime.

At the time, Russia called the accusations "a lie." Syria also disputed the allegations, saying it considered several facilities that were hit to have been taken over by terrorist groups and no longer functioning as medical facilities.

The six incidents the board investigated involved facilities that were destroyed or damaged as a result of military operations and were on a U.N. "de-confliction" list of sites not to be targeted because they involved health and civilian activities, or were supported by the United Nations.

The four attacks in which the board said it was "highly probable" that Syria or its allies were responsible or involved:

—Martyr Akram Ali Ibrahim Al-Ahmad Secondary School in Madiq Castle in Hama governorate on April 28, 2019, which was not on the U.N. "de-confliction" list. The board concluded the school was hit from the air by a fixed-wing aircraft. Nobody was killed or injured.

—Rakaya Primary Health Care Center in Rakaya Sijneh in Idlib on May 3, 2019. The U.N. humanitarian office, OCHA, transmitted de-confliction information to Russia in January 2019. The board said it was "highly probable" a barrel bomb was dropped by a rotary-wing aircraft. A volunteer and others assisting a pregnant woman with her delivery were affected by the blast but did not sustain any injuries.

—Kafr Nobol Surgical Hospital in Kafr Nobol in Idlib on July 4, 2019. OCHA transmitted de-confliction information to Russia in February 2018. The hospital was functioning normally, with about 30 staff members, some patients and their companions, when intense airstrikes began. No one was killed or injured, but the hospital was damaged and had to close for several days.

—Ariha Protection Center for children in Ariha in Idlib on July 28, 2019. OCHA transmitted de-confliction information to Russia in September 2018. Airstrikes on July 27 and July 28 struck near the building, and an explosion in front of the center collapsed its facade and destroyed much of the inside. A staff member who had stayed overnight was hit by falling rubble and had minor injuries.

The fifth incident involved the Kafr Nabutha Primary Health Care Center and Surgical Unit in Kafr Nabutha in Hama, which served an area of about 30,000 people. OCHA had sent de-confliction information to Russia in March 2018. The Syrian regime and its allies launched an offensive in the area around April 27, and the center was damaged, most probably on May 1 and May 7, but no one was killed or injured because it had been evacuated and almost all civilians had fled the area. The board found it "plausible" that the damage "was attributable to the Government of Syria and its allies."

For the final incident, the board said it was "probable" that the attack at the Nayrab Palestinian refugee camp in Aleppo on May 14, 2019, was carried out "by armed opposition groups or by Hayat Tahrir al-Sham." It said 11 people were killed, including five aged 6 to 11, and 29 were injured, 19 seriously.

The board made a series of recommendations including saying "OCHA should directly notify all parties to the conflict, including the government of Syria, of the de-confliction information, unless for security reasons" a partner requests it not to.

Guterres said in his letter some issues the board raised are complex "including the question of which parties to a conflict should be given information intended to support de-confliction." To help determine how best to address the recommendations, Guterres said he plans to appoint "a senior independent adviser with expertise and experience in this area," and was also open to receiving views from the U.N.’s 193 member states.

The board was headed by retired Nigerian Lt. Gen. Chikadibia Obiakor, a former military adviser in the U.N. peacekeeping department. The other members were former senior U.N. refugee official Janet Lim and former U.N. special representative on violence against children Marta Santos Pais.