A high-ranking army officer on Saturday said 160 fighter jets of the types F-16 and F-35 took part in the attack on the so-called 'Metro' system of tunnels during the night.
It was unclear whether any Hamas fighters were killed in the operation. "But potentially they are hundreds," the officer said.
Foreign media have accused the Israeli army of manipulation due to a tweet sent shortly before the attack which stated that Israeli ground troops were in Gaza.
According to media reports, this prompted many Hamas fighters to retreat to the tunnels, after which Israeli jets bombed the Metro network for about 40 minutes.
The army denied a targeted manipulation to create a trap for the militants and spoke of a communication error instead, stressing that no Israeli soldiers had entered Gaza.
The officer said Israel had attacked more than 650 targets in the Gaza Strip since Monday, when the fighting escalated.
He added that 31 workshops to build rockets belonging to the Hamas and Islamic Jihad groups had been destroyed, and Hamas did not have the possibility to build more rockets at the moment.
The aim of the operation was to restore deterrence. "It is very difficult to attack targets in the middle of an inhabited area. But it is the only way to deter Hamas," the officer said.
He said the army was trying not to hit civilian targets, adding that an end to the operation was not yet in sight.
Some 2,300 rockets have been fired from the Gaza Strip towards Israel, although about 20 per cent went down over the coastal enclave without reaching Israeli territory.
Israel said that its Iron Dome defence system successfully intercepted about 90 per cent of the rockets fired.