The United Nations says one of its staff members was killed and another injured as they travelled to a hospital in southern Gaza on Monday, APA reports citing BBC.
It said the workers were travelling in a UN vehicle to the European Hospital near Rafah when it was struck.
The UN did not mention who it thought was responsible for the attack.
The Israeli military said an initial inquiry indicated the vehicle was struck in an active combat zone and it had not been made aware of its route.
Footage posted on social media and verified by the BBC shows a marked UN vehicle with multiple bullet holes outside the European Hospital.
The Israel Defense Forces (IDF) confirmed it had received a report from the UN Department of Safety and Security (UNDSS) that said two of its workers were injured in the Rafah area - in southern Gaza - on Monday.
The IDF added that the incident was under review.
UN secretary-general António Guterres said he was "deeply saddened" to learn of the worker's death and sent his condolences to their family, his spokesman Farhan Haq said in a statement.
"The secretary-general condemns all attacks on UN personnel and calls for a full investigation," Mr Haq added.
Mr Haq said the dead and injured staff members were international workers, not Palestinians, and added he believed the death to be the first of an international UN worker in Gaza since the start of the conflict.
In a separate statement, Mr Guterres said more than 190 UN staff had been killed in Gaza since the war began.
While the worker killed on Monday is thought to be the first international casualty for the UN, six international aid workers and a Palestinian colleague from the international food charity World Central Kitchen were killed in an Israeli strike at the start of April.
Their deaths sparked an international outcry and the IDF sacked two senior officers over the incident which it described as a "grave accident".