Israeli troops took control on Sunday of the major roads leading into Gaza's main population centre as they pushed deeper into the Hamas stronghold, witnesses told AFP.
Infantry units backed by tanks had taken control of Salaheddine Road north and south of Gaza City, they said.
Dozens of tanks operating three kilometres (nearly two miles) south of Gaza City, in the area of the former Jewish settlement of Netzarim, had also taken control of the coastal road, they said.
Explosions rocked the area as the advancing troops exchanged fire with Hamas fighters, who shot off mortar rounds and detonated roadside bombs, they said.
Israeli forces were seen detaining people in the area, they said.