Israeli tanks and troops pressing toward Gaza City met fierce resistance from Hamas fighters using mortars and hit-and-run attacks from tunnels, AFP reports.

“We are at the gates of Gaza City,” said Israeli military commander Brigadier General Itzik Cohen.

Fighters of Hamas and its ally Islamic Jihad were emerging from tunnels to fire at tanks, then disappearing back into the network, residents said and videos from both groups showed, in guerrilla-style operations against a far more powerful army.

“They never stopped bombing Gaza City all night, the house never stopped shaking,” said one man living there, asking not to be identified by name. “But in the morning we discover the Israeli forces are still outside the city, in the outskirts and that means the resistance is heavier than they expected.”

Aware of the difficulties of fighting in an urban environment, Israeli officers’ strategy appears for now to be concentrating large forces in the northern Gaza Strip rather than launching a ground assault on the entire territory.