The two vehicles were used to transport drinking water to residents in the Gaza Strip. Two more people were injured.
"UNICEF calls on the Israeli authorities to immediately investigate the incident and ensure that those responsible are held accountable," the press release reads.
According to UNICEF, it was a routine delivery from a water station used to provide hundreds of thousands of people with clean water.
UNICEF has urged all subcontractors to pause work in the area "until safety can be guaranteed."
