The Israeli military denied that it had hit a clinic in the northern Gaza Strip where health workers were carrying out polio vaccinations, Reuters reports.

On Saturday, the Gaza health ministry said Israeli fire had hit the Sheikh Radwan clinic as parents brought their children in to be vaccinated. It said four children had been wounded in the explosion, which took place during an agreed humanitarian pause to allow the campaign to go ahead.

The military said it was aware of the reports but said an initial review showed its forces had not carried out any strikes when the incident took place.

“Contrary to the claims, an initial review determined that the IDF did not strike in the area at the specified time,” it said in a statement.

The head of the World Health Organization, Tedros Adhanom Ghebreyesus, said the incident had taken place just after a WHO team was at the clinic and that it had endangered a vital health protection campaign.