Israeli media, citing Israeli army, is reporting that nine Israeli soldiers have been killed in Gaza.
Several Hamas-associated X accounts were claiming that Israeli Defence Forces suffered a heavy blow.
Israel said its forces fought Hamas gunmen inside the group's vast tunnel network beneath Gaza as a hospital director said more than 50 Palestinians were martyred in an Israeli air strike on a refugee camp in the besieged enclave.
As the battle inside the tiny Hamas-ruled Palestinian territory intensified, Israeli Prime Minister Benjamin Netanyahu dismissed international calls for a halt to the fighting.
But UN and other aid officials warned that a public health catastrophe was engulfing civilians in Gaza, with hospitals struggling to cope with mounting casualties and food, medicine, drinking water and fuel running short.
The director of Gaza's Indonesian Hospital told reproters that more than 50 Palestinians were killed and 150 wounded in Israeli air strikes on a densely populated area of the Jabalia refugee camp in northern Gaza.