Israeli and Palestinian officials offered conflicting accounts Monday of a blast that killed a 15-year-old boy in Gaza.

Palestinian medical and security sources said the teen was the fourth civilian casualty in four days of Israeli airstrikes, but the Israeli military said it did not attack the area where the death was reported.

"We did not attack during those hours of the morning in the northern Gaza strip," Lt. Col. Avital Leibovich told CNN, saying that Israeli military activity during the time was focused on southern Gaza.

"One of the possibilities is that one of the terrorist organizations in Gaza fired a rocket that landed inside Gaza," Leibovich said, noting that some two dozen rockets fired by Palestinians militants in the last four days have landed inside Gaza.