Photo: The Canadian Press. All rights reserved.

Israeli Defense Minister, Moshe Ya'alon, left, and Israeli Prime Minister Benjamin Netanyahu, center, attend the cabinet meeting at the defense ministry in Tel Aviv, Israel, Thursday, July 31, 2014. (AP Photo/Dan Balilty, pool)

Prime Minister Benjamin Netanyahu said Thursday that Israel will destroy the Hamas tunnel network in the Gaza Strip "with or without a cease-fire," as the military called up another 16,000 reservists to pursue its campaign in the densely-populated territory.

Netanyahu's vow came as international efforts to end the 23-day-old conflict seemed to sputter despite concern over the mounting death toll, with more than 1,300 Palestinians, mostly civilians, and more than 50 Israelis, almost all of them soldiers, killed since July 8.

"We have neutralized dozens of terror tunnels and we are committed to complete this mission, with or without a cease-fire," Netanyahu said. "Therefore I will not agree to any offer that does not allow the military to complete this important mission for the security of the people of Israel."

An initial Israeli aerial campaign against Hamas was widened into a ground offensive on July 17. Since then the campaign has concentrated on destroying more than 30 cross-border tunnels that militants have constructed to carry out attacks on Israeli territory.

Israel says that most of the 32 tunnels it has uncovered have now been demolished and that getting rid of the remainder will take no more than a few days.

The new reserve call-up follows another day of heavy fighting, in which tank shells struck a U.N. school where Palestinians were sheltering and an airstrike tore through a crowded Gaza shopping area. At least 116 Palestinians and three Israeli soldiers were killed Wednesday.

Speaking on condition of anonymity because he was not permitted to discuss the matter with the press, an Israeli defence official said the purpose of the latest call-up was to provide relief for troops currently on the Gaza firing line. However, Israeli officials have also said they do not rule out broadening operations in the coming days.

Fifty-six Israeli soldiers and three civilians on the Israeli side have been killed since the offensive began, as Palestinians have fired hundreds of rockets at Israel -- some reaching major cities -- and carried out attacks through tunnels beneath the heavily guarded frontier.

Israel has called up a total of 86,000 reserves during the Gaza war, which it launched to try to end rocket fire from Hamas and other armed groups.