A polio vaccination centre and the car of a UN aid official involved in this weekend’s vaccination campaign came under fire despite a promised “humanitarian pause” in Israeli bombardment, the UN has said.

Catherine Russell, the executive director of the UN child support and protection agency, Unicef, said: “At least three children were reportedly injured by another attack in the proximity of a vaccination clinic in Sheikh Radwan while a polio vaccination campaign was under way.”

She added that the personal car of a Unicef employee working on the polio vaccine campaign “came under fire by what we believe to be a quadcopter.

“The car was damaged. Fortunately, the staff member was not injured. But she has been left deeply shaken,” Russell wrote. She added that in the previous 48-hour period, more than 50 children had reportedly been killed in the Jabaliya refugee camp, a focus of Israeli military operations over the past month.

“The attacks on Jabaliya, the vaccination clinic and the Unicef staff member are yet further examples of the grave consequences of the indiscriminate strikes on civilians in the Gaza Strip,” Russell said.

“Taken alongside the horrific level of child deaths in north Gaza from other attacks, these most recent events combine to write yet another dark chapter in one of the darkest periods of this terrible war.”

The Israel Defense Forces (IDF) denied responsibility for the reported attack on Sheikh Radwan, which is in northern Gaza to the west of the Jabaliya camp.

“We are aware of a claim about the harm to Palestinian civilians at the Sheikh Radwan vaccination centre in the northern Gaza Strip. Contrary to what was claimed, a preliminary investigation reveals that there was no strike by IDF forces in the area at the time in question,” an IDF statement said.

The weekend’s inoculation campaign was intended to give more than 100,000 Palestinian children under the age of 10 a second dose of polio vaccine, made necessary by an outbreak of the virus reported in July. It had been postponed in late October because of Israeli bombardment.

This weekend, the IDF agreed to suspend its strikes to allow the vaccinations to go ahead in northern Gaza except in the besieged areas in the northern governorate: Beit Hanoun, Beit Lahiya and Jabaliya.

Approximately 15,000 children under 10 are estimated to be in the excluded area and therefore will not receive the inoculation, threatening the effectiveness of the vaccination campaign, which requires at least 90% of all children in every district to be vaccinated to be sure of stopping the spread of the polio virus.

The World Health Organization (WHO) said that 58,604 children had been vaccinated on Saturday, the first day of the campaign. The WHO director-general, Tedros Adhanom Ghebreyesus, described the reported strike on the Sheikh Radwan clinic as “extremely concerning”, saying it had happened “while parents were bringing their children to the life-saving polio vaccination in an area where a humanitarian pause was agreed to allow vaccination to proceed”.

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“A WHO team was at the site just before,” Ghebreyesus said on the X social media platform. “This attack, during humanitarian pause, jeopardises the sanctity of health protection for children and may deter parents from bringing their children for vaccination. These vital humanitarian-area-specific pauses must be absolutely respected.”

The Israeli prime minister, Benjamin Netanyahu, visited Israel’s northern border with Lebanon on Sunday, where he said that Hezbollah must be pushed back beyond the Litani River, with or without a ceasefire deal in place, and that the Iran-backed group must be prevented from re-arming.

“With or without an agreement, the key to returning our (evacuated) residents in the north safely to their homes is to keep back Hezbollah beyond the Litani, to strike its every attempt to rearm, and to respond forcefully against all action against us,” Netanyahu said during a visit to the border. The river is roughly 30km (20 miles) inside Lebanon from the border with Israel.

The Israeli army said Hezbollah had fired about 60 rockets across the Lebanese border on Sunday, some aimed at the occupied Golan Heights, others at the western Galilee area.

The IDF said most of the projectiles were intercepted and those that got through Israeli defences fell in open areas, causing no casualties on this occasion. The IDF, meanwhile, issued evacuation warnings to Lebanese residents in some areas of the ancient city of Baalbek and said that buildings being used by Hezbollah militants would be targeted imminently.

The death toll from Israeli attacks on Lebanon has now climbed to 2,897 and the number of injured to 13,150 since October 2023, including 30 dead and 183 injured in the past 24 hours, the Lebanese health ministry said.