The French foreign ministry said one of its workers had died as a result of wounds sustained during an Israeli attack in Rafah, in the south of the Gaza Strip.
The man was seeking refuge in the house of a colleague from the French consulate alongside two other co-workers and a number of their family members, the ministry statement issued late on Saturday said.
"The house was hit by an Israeli air strike on Wednesday evening, which seriously hurt our agent and killed about 10 others," it said, adding he had later died of his wounds.
The statement said France condemned the bombing of a residential building.
"We demand that the Israeli authorities shed full light on the circumstances of this bombing, as soon as possible," it said.
The Israeli military did not immediately respond to a request for comment. A spokesperson for the French foreign ministry declined to provide further details on the name, nationality and age of the worker.
"We're waiting for clarification (from Israel)," said French Foreign Affairs Minister Catherine Colonna shortly after meeting her Israeli counterpart Eli Cohen in Tel Aviv on Sunday.
She called for an "immediate truce" between Hamas and Israel to allow for a humanitarian ceasefire.
Israel says it seeks to protect civilians and civilian infrastructure, according to international law, though critics and even its closest ally, the U.S., say it needs to do more.