Israel launched a ground operation in Gaza late Thursday on the 10th day of an offensive to stamp out rocket attacks from the Palestinian enclave, the Israeli army said, as the death toll in Gaza rose to at least 240 and efforts to reach an Egypt-mediated ceasefire collapsed.

"Following 10 days of Hamas attacks by land, air and sea, and after repeated rejections of offers to deescalate the situation, the Israel Defense Forces (army) has initiated a ground operation within the Gaza Strip," it said in a statement.

The army said the aim of the operation is to protect Israeli lives and crush Hamas, which controls the Gaza Strip.

"The IDF's objective as defined by the Israeli government is to establish a reality in which Israeli residents can live in safety and security without continues indiscriminate terror, while striking a significant blow to Hamas' terror infrastructure," the statement said.

Israel launched Operation Protective Edge on July 8 to stamp out rocket attacks from Gaza and the army said the new operation will include ground and air assaults.

"This stage of operation 'Protective Edge', led by the IDF's Southern Command, will include close coordination between IDF units including infantry, armored corps, engineer corps, artillery, and intelligence combined with aerial and naval support," it said.

"This effort will also be supported by the Israeli Security Agency (ISA) and other intelligence organizations," the army added.

"In the face of Hamas' tactics to leverage civilian casualties in pursuit of its terrorist goals, the IDF will continue in its unprecedented efforts to limit civilian harm," it said.

At least 240 Palestinians have been killed in Israeli air strikes since July 8, many of them children, medics in Gaza said, with a NGO based in the coastal enclave saying 80 percent of the deaths are civilians.

Israeli tank fire in Gaza killed three people on Thursday night.

The three were killed in east Gaza, said emergency services spokesman Ashraf al-Qudra, who added that they were a four-year-old child, a 15-year-old, and a man aged 26.

Their deaths came after a strike that killed three children in the Sabra neighborhood of central Gaza -- Jihad, Waseem and Fulla from the Shuheiber family.

Their deaths were the first to follow the end of a five-hour humanitarian ceasefire, which brought some respite for residents of the besieged Palestinian territory.

Another strike shortly afterwards in the southern city of Khan Yunis killed four-year-old girl Rahaf al-Jubur, and a 29-year-old man, Hamza al-Abadleh.

And another child died of wounds sustained in an earlier strike in Gaza City, Qudra said.

Before the ceasefire took effect at 10:00 (0700 GMT), Israeli tank fire killed three men in their twenties in the southern city of Rafah, Qudra said.

One Israeli has also been killed by rockets fired by Palestinian militants.

On the Palestinian side, 1,690 people have been injured during the conflict, Qudra said.

In its air war aimed at halting the rocket fire, Israel has struck more than 1,750 so-called "terror targets" across the coastal enclave, the army said.

Also on Thursday, Israel shot down a Hamas drone near the southern city of Ashkelon close to the Gaza border, in the second such incident this week, the military said.

"Aircraft detected an unmanned plane and it was intercepted with a surface-to-air Patriot missile near Ashkelon," it said in a statement.

Ezzedine al-Qassam Brigades, the armed wing of Hamas, said it launched the drone on an “attack mission” over central Israel.

On Monday, Hamas boasted that it had launched a drone flight deep into Israel, targeting the defense ministry in the heart of Tel Aviv. The Israeli army confirmed it had shot down an unmanned aircraft but said it was intercepted well south of Tel Aviv.

Meanwhile, Israeli tanks shelled Gaza's al-Wafa hospital, whose 14 patients include some who are paralyzed or in a coma, and several people have been hurt, the facility's director said.

"Israeli tanks are shelling the hospital, they have hit several of the floors, and several nurses have been injured," director Basman Alashi told AFP.

The hospital in Gaza's Shejaiya district has come under Israeli fire several times before, and the Israeli military has called on Alashi and other doctors to evacuate it.

Alashi told AFP on Wednesday that it was almost impossible to move the patients, most of whom are immobile, and he questioned where they could go.

"There is no place safe in Gaza! If a hospital is not safe, where is?" he said.

On Thursday night, he said he was contacting other hospitals in Gaza to try to arrange ambulances to transport the 14 patients elsewhere after al-Wafa came under renewed Israeli fire.

"But the ambulances are all in use, there is heavy shelling in many places," he said.

"And each patient has to be taken individually and carried because they cannot move."

"They are tearing the hospital apart, bit by bit."

Meanwhile, Egypt's foreign minister said Hamas could have saved dozens of lives if it had accepted a Cairo-mediated truce earlier this week.

"Had Hamas accepted the Egyptian proposal, it could have saved the lives of at least 40 Palestinians," Sameh Shoukri said, quoted by state news agency MENA.

Earlier on Thursday, a Hamas official denied that a ceasefire deal with Israel had been reached, rejecting claims from an Israeli official that they had agreed to halt fire early Friday, as the overall death toll from 10 days of Israeli bombardment against Gaza rose to 237.

"The news about a ceasefire is incorrect. There are continuing efforts but no agreement until now," Hamas spokesman Sami Abu Zuhri told Agence France Presse.

The denial came after an Israeli official who spoke to AFP on condition of anonymity said the Jewish state had agreed a ceasefire with Hamas that would begin at 0300 GMT on Friday.

Meanwhile, a rocket fired from Gaza hit the Israeli city of Ashkelon on Thursday, the Israeli army said, just as a five-hour truce ended.

The rocket hit at exactly 3:00 pm (1200 GMT), the army said in a statement, after the two sides had agreed to cease hostilities on humanitarian grounds for five hours from 0700 GMT, at the request of the U.N.

Later, Israeli warplanes struck an open area in northern Gaza in the first air strike since the end of the truce, witnesses said.

The strike in Beit Lahiya hit an open area, causing no injuries.

Meanwhile, Hamas' armed wing, the Ezzeddine al-Qassam Brigades, announced firing two M75 rockets at Tel Aviv.

Earlier in the day, three mortar shells fired from Gaza hit southern Israel, the army said, just over two hours after a humanitarian ceasefire took effect.

The shells struck in the region of Eshkol, which borders the southern Gaza Strip, the army told AFP, blaming Hamas but without giving further details.

There were no immediate reports of any damage or casualties. Hamas denied any involvement in the attack.

"They (Israelis) are lying. All the Palestinian factions are continuing to observe the truce," a Hamas source told AFP, speaking on condition of anonymity.

"They want to use this as a reason to kill fighters," the source said.

The army later said an explosion near the border wounded one soldier, without giving any details of the location of the blast. The military responded with artillery fire.

Speaking on condition of anonymity, an Israeli official had told AFP that Israel and Hamas "have agreed upon a ceasefire that will begin at 6:00 am tomorrow."

But Hamas spokesman Fawzi Barhum told AFP the Palestinian movement had “no information about this agreement.”

Another Hamas spokesman, Ihab Ghussein, said there were talks and contacts under way but dismissed reports of a deal.

"The killing by the Israelis should stop before talking about any ceasefire," he told AFP.