GAZA CITY, Gaza (CNN) -- The main humanitarian aid group for the United Nations in Gaza has suspended activities in the Palestinian territory, its chief spokesman said Thursday.
The move comes after a U.N. Relief and Works Agency truck driver was killed and two other people were wounded by an Israeli tank shell near the Erez Crossing, said Adnan Abu Hasna, a spokesman for the U.N. agency in Gaza.
A spokeswoman for the Israeli military said it is not aware of the attack but said Hamas militants sometimes have targeted U.N. aid trucks to take food.
The U.N. relief agency will suspend activities until the Israeli military can guarantee the safety of its staff, said the agency's chief spokesman, Chris Gunness, in Jerusalem.
The U.N. agency provides food and relief supplies to about 80 percent of Gaza's 1.5 million people.
Israeli artillery and missiles have struck three U.N. schools in Gaza this week. More than 40 civilians were killed in a strike Tuesday on a U.N. school in Jabalya that was being used as a shelter. Three people were killed in airstrike Monday on a school shelter in Gaza City.
Israeli Foreign Ministry spokesman Yigal Palmor said Israeli forces fired on Hamas militants in "the immediate vicinity" of the Jabalya school. Gunness vehemently denied any militants were inside the school and demanded that Israel agree to an impartial investigation.