“Israel’s airstrikes and ground operations in a crowded refugee camp were the worst violence in the West Bank in many years,” said António Guterres, referring to the two-day-long military assault in Jenin, which began on Monday morning, involving the use of airstrikes and missiles fired from drones.

According to the Palestinian health ministry, 12 people were killed, including three children, during what Israel described as a counter-terror operation. At least 120 were wounded, including 20 still in critical condition.

Gun battles broke out between Israeli forces and Palestinian militants, with some roads torn up and many homes and properties damaged. At least 3,000 people were reportedly forced to flee their homes.

A car ramming attack in Israeli’s largest city, Tel Aviv, in apparent retaliation for the Jenin operation left nine injured. The Palestinian man who drove the vehicle into pedestrians was shot dead at the scene.

On Thursday, Israel said it had responded with artillery fire after a rocket was launched into Israeli territory from southern Lebanon.

Exercise restraint

Addressing correspondents at UN Headquarters in New York, the Secretary-General noted that schools and hospitals had been damaged in Jenin along with water and electricity networks.

“All those injured must have access to medical care, and humanitarian workers must be able to reach everyone in need," he said. "I once again call on Israel to abide by its obligations under international law, including the duty to exercise restraint and use only proportional force and the duty to minimize damage and injury and respect and preserve human life.”

He described the use of airstrikes as “inconsistent with the conduct of law enforcement operations”, and reminded Israel that as the occupying Power, it is responsible for ensuring civilians are “protected against all acts of violence”.

More violence ‘is not the answer’

Mr. Guterres said he understood Israel’s legitimate concerns over its security, “but escalation is not the answer; it simply bolsters radicalization and leads to a deepening cycle of violence and bloodshed.”

He said it was in Israel’s long-term interest to abide by the two-State solution, which envisages an independent Palestine next door.

“Restoring the hope of the Palestinian people in a meaningful political process, leading to a two-State solution and the end of the occupation, is an essential contribution by Israel to its own security.”

Watch the UN chief's full remarks at the UN Security Council stakeout, where he also speaks about the crisis in Haiti: