RNA - The UN chief said in a report obtained by news agencies that he is "shocked" by Israel's use of live fire since border rallies began in Gaza in late March, Al-Jazeera reported.
Guterres stated that its military has "a responsibility to exercise maximum restraint" except as a last resort.
The report was sent to the council last week in advance of a meeting on Tuesday on the Israeli-Palestinian conflict.
"The killing of children, as well as of clearly identified journalists and medical staffers by security forces during a demonstration are particularly unacceptable," Guterres said, adding that "they must be allowed to perform their duties without fear of death or injury".
Israel has not yet responded to the accusations.
Guterres also told the Security Council that he "unequivocally condemns the steps by all parties that have brought us to this dangerous and fragile place" in the Israeli-Palestinian conflict.
Since weekly mass protests began along the Israel-Gaza border on March 30, at least 130 Palestinians have been killed and 13,000 others wounded by Israeli army fire. The overwhelming majority of the dead and wounded have been unarmed, according to Gaza health officials. Two Palestinian journalists were killed while covering the protests in April and two medics including a 21-year-old were also shot dead in May and early June.