The Gaza Health Ministry is the main source of data you read about in Reuters and AFP. Hamas also runs a media office that provides official statements on airstrikes, casualties and other events. They have a history of suppressing and intimidating journalists, and they have a history of propaganda.

There are no foreign journalists in Gaza. The journalists you're referring to are Palestinian freelance journalists. Those journalists are working in a media landscape controlled by terrorists. For example they wouldn't be permitted to report back to Reuters about Hamas policing or regrouping.