GAZA CITY, Palestinian Territories - Israel began a ground operation in Gaza as a deadly offensive to stamp out rocket fire from the Hamas-run enclave that has cost 247 Palestinian lives entered its 11th day Friday.
The late Thursday assault follows a brief humanitarian truce and an urgent appeal by both Washington and the UN that Israel redouble its efforts to avoid harm to civilians.
"I regret that despite my repeated urgings, and those of many regional and world leaders together, an already dangerous conflict has now escalated even further," UN chief Ban Ki-moon told reporters, urging Israel to "do far more" to spare Palestinian civilians.
Hamas said the ground operation was destined to fail and that Israel would pay a high price.
"What the occupier Israel failed to achieve through its air and sea raids, it will not be able to achieve with a ground offensive. It is bound to fail," Hamas chief Khaled Meshaal from his exile in Doha.
A Hamas spokesman in Gaza earlier said "Israel will pay a high price" for launching the ground operation and that his Islamist movement "is ready for the confrontation".
"Following 10 days of Hamas attacks by land, air and sea, and after repeated rejections of offers to de-escalate the situation, the Israel Defence Forces (army) has initiated a ground operation within the Gaza Strip," the army said.
Israel approved the call-up of another 18,000 reservists, taking the total number approved to 65,000 for an operation aimed at protecting Israeli lives and strike "a significant blow to Hamas's terror infrastructure," the army said.
Shortly beforehand, the military began an intensive bombardment of Gaza by air and sea as well as by tanks massed along the border.
Salvoes of rockets lit up the sky, and a seafront hotel in Gaza City housing scores of journalists shook violently with the force of the shelling by sea, an AFP correspondent said.
Israel launched Operation Protective Edge on July 8 to stamp out rocket fire from Gaza, pounding the enclave from both the air and the sea.
Egypt lashed out at Hamas on Thursday, saying it could have saved dozens of lives had it accepted an truce brokered by Cairo but also condemned the "Israeli escalation.
"Had Hamas accepted the Egyptian proposal, it could have saved the lives of at least 40 Palestinians," said Egypt's Foreign Minister Sameh Shoukri.
An initial ceasefire proposal which was to begin on Tuesday was accepted by Israel but ignored by Hamas, which continued to fire rockets over the border.