UN Secretary-General Antonio Guterres has warned that the “most serious escalation” of violence in the Gaza Strip places the besieged enclave on the “brink of war”, urging Israel and Hamas to recommit to a 2014 ceasefire.

The UN chief said in a report obtained by news agencies that he is “shocked” by Israel’s use of live fire since border protests began in Gaza on 30 March.

Guterres said its military has “a responsibility to exercise maximum restraint” except as a last resort.

The report was sent to the council  in advance of a meeting 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.

“They must be allowed to perform their duties without fear of death or injury.”

Israel has not yet responded to the accusations.

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.

Guterres renewed his call for an independent and transparent investigation of the shooting deaths in Gaza. Israel, which says Hamas has used the protests as cover for attacks on the border fence, has rejected the appeal and argued that the use of force is justified to defend its borders.

The marchers have pressed demands for a right of return for Palestinian refugees to their families homes which they were forced to flee 70 years ago.

More than 700,000 Palestinians were expelled or fled in the 1948 war over Israel’s creation. Two-thirds of Gaza’s two million residents are internally displaced people.

He also expressed concern over the deteriorating humanitarian situation and economic collapse in Gaza, marked by a “severe liquidity crisis and an acute shortage of cash”.