Gaza City (CNN) -- The battle between Israel and Gazan militants is growing, as the Israel Defense Forces announced early Sunday that it will expand its ground offensive.
On Saturday, Hamas Islamist fighters infiltrated nearby parts of Israel via underground tunnels and clashed with Israeli troops. The use of the tunnels was the main reason Israel gave for launching its ground operation Thursday night.
The IDF is adding additional troops, having called up tens of thousands of reservists at the start of Operation Protective Edge to prepare for the ground operations.
"In preparation for the mission, the forces have undergone an intensified training and thorough planning period and are prepared and stand ready for the task at hand," said IDF spokesman Lt. Col. Peter Lerner in a statement.
The IDF's goal is to weaken Hamas military capabilities, the statement said.
The clashes demonstrated how Israel's conflict with Hamas has now spilled outside -- and even underneath -- Gaza as the ground war entered a third night Saturday.
As midnight approached, a major battle flared in Shaja'ia east of Gaza City, where the horizon along the border was dominated with flashes, explosions and columns of smoke.
Sixty-two people in Gaza had been killed Saturday, the highest daily death toll so far, according to the Gaza Health Ministry.
An example of infiltration occurred earlier in the day when Hamas militants slipped out of a tunnel from central Gaza and fired at Israeli soldiers, killing two of them, Israel's Channel 10 said.
The Hamas gunmen disguised themselves in uniforms belonging to the Israel Defense Forces, the military said.
One of the Hamas gunmen was killed on Israeli soil, and the rest fled back to Gaza and were killed by a helicopter gunship, Channel 10 said.
"We know that Hamas terrorists are operating underground, and that's where we will meet them," the IDF said in a statement.
The IDF said it found 13 tunnels across Gaza, with 34 access points.
In another infiltration, a dozen Hamas fighters penetrated an Israeli military base they called Abu Mutibq and ambushed a convoy of Israeli troops just outside Gaza, killing six Israeli soldiers, according to Hamas' military wing, the al-Qassam Brigades.
Several more Israeli soldiers were wounded, the militants also claimed.
Hamas fighters had lain in wait for the convoy for six hours, the militants said.
"Our fighters could have at any given time raided the settlements in the area, but we in the al-Qassam Brigades started the clash with the enemy soldiers to teach him a practical lesson from direct contact," Hamas' military wing said in a statement.
In that attack, three Israeli military jeeps were destroyed, and another fled, the Hamas brigades said. Two Israeli M-16s were seized, Hamas said.
Hamas militants also claimed to have infiltrated behind Israel's front lines east of Rafah. The al-Qassam Brigades claimed to have killed an unspecified number of Israeli soldiers.
In one of the foiled infiltrations, a killed Hamas fighter was found with tranquilizers and cuffs, "carried with intention to abduct Israelis," the Israeli military said.
Living with tank and air strikes
The changing battlefied came as 62 more people died Saturday in Gaza, according to territory health officials. The overall toll there has reached 373 since the Israeli military operation Protective Edge began July 8. A fifth of those deaths are children.
More than 70% of those killed have been civilians, according to the United Nations.
The Israeli military said late Saturday that since its ground war began Thursday, at least 70 "terrorists" were killed, including 20 in the past 24 hours. Thirteen more fighters were captured and brought to Israel for questioning.
While the battle grew geographically, the brunt of the conflict remained focused on Gaza, where Palestinian civilians say there's nowhere for them to hide in the densely populated coastal enclave.
Residents have quickly learned how to recognize the differences in gunfire -- and which means a better chance of survival.
In his Gaza home, Ramez al-Madhoun listened Saturday to the thunder of Israeli tank shells battering the neighborhood -- some a little less than a mile away, some closer.
A few miles south of him, militants' rockets streamed into the sky -- about seven in 15 minutes -- toward Israel.
The tanks were gunning for tunnels leading into Israel and the Gazan attack squads that use them.
Al-Madhoun said he felt safer during Israeli airstrikes.
"If it was an airstrike, it would be more of a precision strike, but the tanks shells are more dangerous. They are destroying more than the airstrikes," he said.
Every 30 seconds to a minute, a shell landed in or around Beit Lahya. The local imam has told residents to stay home and pray, because the shelling has made it too dangerous to go outside, al-Madhoun says.
Farther to the south, the Israeli military also encountered a suicide donkey -- one loaded with explosives -- approaching soldiers near Rafah. The troops fired on the animal, detonating the bombs and killing the donkey Friday night. Fighting raged there Saturday with Hamas brigades shelling an armored vehicle, Hamas said.
Meanwhile, Palestinian Authority President Mahmoud Abbas will travel to Qatar on Sunday and may meet with Hamas leader Khaled Meshaal, though a meeting hasn't been confirmed, said Izzat Risheq, a senior aid to Khaled Mashaal and a member of Hamas political bureau.
In southeastern Israel, a rocket from Gaza crashed into Negev early Saturday, killing an Israeli, the Israel Defense Forces reported.
The rocket wounded four others, a hospital spokesman says. One of them is a 3-month-old; its wounds are severe.
Two Israelis have been killed by apparent Hamas rockets in the past week's warfare.
In Gaza, the al-Qassam Brigades announced that it sent an attack squad to Eshkol, just on the other side of the border. The IDF has the entire district, or regional council, under military lockdown to avoid Israeli civilian deaths.
But next to Eshkol's Kibbutz Beeri, a militant squad popped up out of tunnel to carry out an attack. They quickly crossed paths with an IDF patrol, and a firefight erupted, the IDF says. It wasn't immediately clear whether the clash was related to another reported infiltration.
A Palestinian militant was killed and four Israeli soldiers injured. The IDF pushed the rest of the attackers back into Gaza, where the air force pursued them farther.
Then, sirens howled an incoming rocket warning over Eshkol. The two missiles fell into open areas.
Warnings also sounded Saturday about missiles over the Israeli cities of Ashkelon, Rishon Letzion, Rehovot and Beer Sheva. The rocket aimed at Beer Sheva exploded in an unpopulated area.
1,770 rockets, 2,300 strikes
Since Operation Protective Edge began, militants in Gaza have launched 1,770 rockets, the IDF said in a statement Saturday. The Israeli rocket defense system Iron Dome has intercepted 360 of them.
The IDF has struck "2,300 terror targets" in Gaza, the statement said. In its recently launched ground operations, the IDF targeted 95 rocket-launching sites and found 13 tunnels with a network of at least 34 shafts.
Hamas-run Al-Aqsa TV reported Friday that Israel had sent text messages to many Palestinians telling them of safe corridors to reach central Gaza.
Before the land incursion, the IDF dropped leaflets in 14 areas of Gaza, urging residents to temporarily leave their homes. But many have nowhere to go in the small, impoverished strip of land. Border crossings with Israel and Egypt are closed.
"The IDF is a moral military without peer; it does not aspire to harm any innocent person," Israeli Prime Minister Benjamin Netanyahu said before a special Cabinet meeting Friday. "We are operating only against terrorist targets, and we regret any inadvertent civilian casualties. It is the terrorist organizations -- which attack our cities and our civilians and use their civilians as human shields -- that bear the responsibility for casualties among noncombatants."
The new warfare in Gaza, however, has displaced more than 61,479 Palestinians, a figure harkening to the peak number from Israel's Operation Cast Lead in Gaza in 2008-09. It killed 1,166 Palestinians, including 709 Hamas operatives, according to the United Nations.
Health ministry: 72 of the dead in Gaza are children
The flash of assorted ordnance illuminated Gaza's night sky on Friday as Israeli forces and Hamas militants clashed throughout the 27-mile-long Palestinian territory.
With fighting reported all along the coastal enclave, casualties poured into Gaza City's Shifaa Hospital, including children, after Israeli artillery shelled east of the city, physicians told Al-Aqsa TV.
Children are 72 of the dead, said Gaza health ministry spokesman Dr. Ashraf al-Qedra. About 2,560 people in Gaza have been injured in the fighting.
Hospitals say they are running out of emergency medical supplies.
On Saturday, five Israeli trucks delivered 100 tons of medicine and supplies for Gaza hospitals, the military said.
A family of eight died when Israeli artillery shells hit their northern Gaza home, the health ministry said.
It's the region where al-Madhoun lives, which borders on two sides with Israel. He can hear automatic gunfire in the distance.
Netanyahu has warned that Israeli ground troops are prepared to expand an offensive against Hamas militants after Hamas rejected an Egyptian-backed cease-fire proposal.
Hamas leaders complained that they had not been consulted on the deal. They wanted Israel to free Palestinian prisoners and to ease a border blockade that has been in effect for much of the past seven years on Gaza.
"Look, we have some demands," senior Hamas spokesman Ghazi Hamad said. "They should listen to us. We are not against this cease-fire. We want to live. We want to be also in a good situation."
No water, some food
In Beit Lahya, Al-Madhoun can't get to his well to get water. His pumps are electric, and Friday's fighting knocked out power. It surges back for a few moments at a time, but it's hardly reliable.
He has to wait for rations.
"The water from the municipality is going to be distributed to us for two hours in a 24-hour cycle," he said.
If there is a break in the shelling, he can go south to Jabalya, where it's less dangerous, to stock up on food. He goes every two or three days.
"We don't know when that will run out," he said.
CNN's Michael Martinez reported and wrote from Los Angeles and Ben Brumfield from Atlanta. CNN's Ben Wedeman reported from Gaza City. CNN's Kareem Khadder, Ian Lee, Ali Younes, Ralph Ellis, Tim Lister, Diana Magnay, Samira Said, Michael Schwartz, Salma Abdelaziz and Tal Heinrich contributed to this report.