TEL AVIV—The Israeli army expanded its ground raids and intensified airstrikes in Gaza during a communications blackout in the strip Friday night, its most significant operation yet ahead of an expected invasion intended to end 16 years of Hamas rule.

With tanks, artillery and tens of thousands of troops massed on the strip’s border, Israeli officials said Friday they were moving closer to starting a major ground invasion in response to the Oct. 7 attacks that could take months, expose soldiers to dangerous urban warfare and raise the already mounting civilian death toll.