Pope Francis expressed his "deep sorrow" Wednesday for the deaths of seven charity workers killed by an Israeli strike while they were delivering aid in Gaza.

"I express my deep sorrow for the volunteers killed while they were distributing humanitarian aid in Gaza," the 87-year-old pontiff said during his weekly audience at the Vatican. 

"I pray for them and their families." 

He renewed his appeal for access to humanitarian aid for the "exhausted and suffering civilian population" of Gaza, and for the hostages taken by Hamas to be released. 

Israel's defense chief on Wednesday described the strike on staff from World Central Kitchen as a "grave mistake", after the deaths prompted a chorus of international outrage. 

The bloodiest-ever Gaza war erupted with Hamas's 7 October attack, which resulted in about 1,160 deaths in Israel, mostly civilians, according to an AFP tally of Israeli official figures. 

Israel's retaliatory campaign has killed at least 32,916 people, mostly women and children, according to the health ministry in Hamas-run Gaza. 

During their attack on Israel, Palestinian militants also seized around 250 hostages. Israel believes about 130 remain in Gaza, including 34 who are presumed dead.