The army will continue working to destroy tunnels used by Gaza fighters for cross-border attacks with or without a ceasefire, Israeli Prime Minister Benjamin Netanyahu said on Thursday.

"Until now, we have destroyed dozens of terror tunnels and we are determined to finish this mission -- with or without a ceasefire," he said in a live address at the start of a cabinet meeting.

"So I will not accept any (truce) proposal that does not allow the IDF (army) to complete this work for the security of Israel's citizens."

Israel began its military offensive in Gaza on July 8 with the aim of stamping out persistent rocket fire on southern Israel, but expanded the operation by sending in ground troops on July 17 to destroy a sophisticated network of tunnels used by fighters.

Since the operation began, Netanyahu has called for the Gaza Strip to be demilitarised and he said destroying the tunnels was a first step towards that.

"This is only the first stage in the demilitarisation of Gaza," he said, indicating that Israel's position on the need to destroy the tunnels had been accepted by Washington, Brussels and other key diplomatic players.

Even as troops have worked to destroy the tunnels, some of which have been booby trapped, fighters have managed to use them to infiltrate southern Israel five times, Haaretz newspaper reported on Thursday.