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Damascus, Syria (CNN) -- The growing presence of Islamic fundamentalist fighters is among the "most alarming" trends in Syria's civil war, a United Nations investigator said Monday.
"Some of them can be classified as jihadis," said Paulo Pinheiro, who chairs an independent international committee charged with investigating the situation in Syria. "Sometimes they fight together with some armed groups of the opposition. Other times they go by themselves. They have their own agenda."
Hours after presenting a new report to the U.N. Human Rights Council in Geneva, Switzerland, Pinheiro told CNN that the fundamentalist fighters were "one of the most alarming elements in the present stage of the civil war in Syria."
The commission also believes both sides of the conflict have committed war crimes, according to the report Pinheiro presented Monday.
"The commission found reasonable grounds to believe that government forces and the (Shabiha) had committed the crimes against humanity of murder and of torture, war crimes and gross violations of international human rights law and international humanitarian law, including unlawful killing, torture, arbitrary arrest and detention, sexual violence, indiscriminate attack, pillaging and destruction of property," a summary of the report states. Shabiha are pro-government militia.
In addition, "The commission found reasonable grounds to believe that war crimes, including murder, extrajudicial execution and torture, had been perpetrated by organized anti-government armed groups."
Pinheiro told the council that "gross violations of human rights have grown in number, in pace and in scale."
At the meeting, Syria's representative said the commission's report "was neither accurate nor objective," according to a summary from the United Nations.
Speaking to reporters later Monday, a spokesman for France's Foreign Ministry said the report was "damning for the Damascus regime."
"We are looking at ways to ensure that the matter is referred to the International Criminal Court by the Security Council," spokesman Philippe Lalliot said.
In another report released Monday, Human Rights Watch said that armed opposition groups have "subjected detainees to ill-treatment and torture and committed extrajudicial or summary executions."
In other developments:
Many Syrian children can't go to school
The school year officially starts this week in Syria, but the reality of war prevents thousands of children from learning.
More than 2,000 of the country's 22,000 schools have been damaged or destroyed, according to the Syrian Ministry of Education.
The education crisis extends beyond Syria's borders.
The Lebanese government was working to place an estimated 32,000 refugee children in public schools, the United Nations Children's Fund said.
At the Zaatari refugee camp in Jordan, UNICEF was registering school-age children while working to build a school that can accommodate up to 5,000 students, the agency said.
For some children inside Syria who can't go to school, UNICEF provided "recreational kits because these children had nothing to do."
At least 142 people were killed in violence across Syria on Monday, the opposition Local Coordination Committees of Syria said. The toll included 50 dead in Damascus and its suburbs and 31 more in Aleppo, the country's commercial capital.
CNN could not independently confirm those figures, which do not include deaths of government forces.
The state-run Syrian Arab News Agency reported Monday that operations "against terrorists" were continuing throughout the country.
Dozens were killed in clashes in Aleppo, the government news agency said Monday. Authorities also "inflicted heavy losses" in fighting with gunmen who tried to attack a security checkpoint in Homs, the news agency said.
CNN's Saad Abedine and Salma Abdelaziz contributed to this report.