Hamas militants intensified their attacks on Israeli forces Saturday, killing two soldiers on Israeli soil and attacking others with antitank missiles, machine guns, even an explosives-laden donkey, apparently undaunted by Israel’s incursion into the Gaza Strip.

As the conflict stretched into its 12th day, the militants’ resilience seemed to upend the narrative provided by Israel of a Hamas severely weakened by the Israeli ground offensive, airstrikes, artillery barrages and the ongoing destruction of its tunnel network.

In their most audacious attack Saturday, Hamas fighters dressed in Israeli army uniforms slipped from central Gaza into Israel through a tunnel and attacked an Israeli army patrol, killing two soldiers and injuring two others. The army returned fire, killing one militant and forcing the rest back through the tunnel into the Palestinian territory.

In all, three Israeli soldiers have been killed since the ground offensive began Thursday night.

Hamas, military analysts said, is much better prepared militarily than in its two previous conflicts with Israel, in 2009 and 2012. Since then, the Islamist group has invested millions in building large quantities of short- and long-range rockets, as well as acquiring other sophisticated weaponry.

At the same time, Hamas’s political and economic situation is in its worst state since the group seized control of Gaza in 2007. It no longer has the support of Iran, Syria or Lebanon’s Hezbollah militia because of its refusal to back President Bashar al-Assad in Syria’s civil war. In Egypt, the Muslim Brotherhood, of which Hamas is an offshoot, is no longer in power. Much of the Arab world, in fact, no longer supports the militants, crippling them financially.

“They are really stressed. They have to work very hard to achieve meaningful or strategic developments,” said Kobi Michael, former head of the Palestinian desk at Israel’s Ministry of Strategic Affairs.

“They are much more violent and extremist than in previous campaigns,” he added.

In a second attempt Saturday to enter Israel through their tunnels, Hamas militants were found carrying handcuffs and tranquilizers in an apparent attempt to kidnap soldiers, Israel’s military said, adding that the militants were killed. In a third incident, a militant emerged from a concealed tunnel entrance in southern Gaza and began firing at soldiers.

Saturday’s attempted infiltrations into Israel, coming as thousands of Israeli soldiers focus on dismantling the Hamas tunnel network along Gaza’s border, suggested that the number of tunnels could be far greater than believed. If Hamas continues to use them to kill and injure Israeli soldiers or target civilians in Israel, it could prompt Israel to widen its ground offensive and push deeper into Gaza, swelling civilian casualties.

The Palestinian death toll from the conflict rose Saturday to more than 330, including about 60 children, according to the Gaza Health Ministry. An additional 2,200 have been injured. The United Nations estimates that about 80 percent of the casualties are civilians, many of them children.

More than 60,000 Palestinians are seeking refuge in U.N. shelters. By Saturday, large swaths of the coastal enclave, including Gaza City, had been without electricity for 24 hours. Residents worry about their water supply, since they need electrical power to pump water to their rooftop tanks.

Citing its concern about reports of severe shortages of medicines, Israel briefly opened its Erez crossing into Gaza to allow medical supplies in.

Israeli troops and Gaza militants engaged repeatedly in exchanges of small-arms fire.A midday gun battle near the no-man’s land between the fence and populated areas in central Gaza left several Israeli soldiers injured. An overnight attack by a militant near Beit Lahiya wounded three Israeli soldiers. And in southern Gaza, three more soldiers were injured when an explosive device planted by Hamas militants detonated.

“The resistance is roughly as we were expecting, maybe a little bit lower,” a senior Israeli military official told reporters Saturday, speaking on the condition of anonymity in accord with military protocol. “We expect Hamas to fight.”

In one incident, militants strapped a donkey with explosives and pushed it in the direction of Israeli soldiers, Israel’s military said, adding that soldiers “engaged the donkey and it exploded at a safe distance” without injuring any troops.

Much of Hamas’s ammunition and weaponry has been smuggled in from Iran or Sudan, through tunnels that stretched from Egypt into Gaza, according to Israeli intelligence officials. So were raw materials used by Hamas engineers to assemble sophisticated homemade rockets and other weapons. There are also reports that Hamas has acquired drones.

But since the ousting of the Muslim Brotherhood last year, Egypt’s military has destroyed most, if not all, of the tunnels entering Gaza and closed off its border.

A high-ranking Israeli intelligence officer told reporters in a briefing Saturday that Hamas’s fighters were unable to match Israel’s firepower and that Israel was “using its power on the ground to ruin those tunnels.” He said Hamas’s weapons arsenal had been reduced by about half and that the Israeli army “believes that it has caused a lot of damage” to the group.

Still, as they tangled with Israeli troops on the ground, Hamas and other militant factions continued to fire a steady barrage of rockets from the Gaza Strip into Israel.

Since Israel’s ground offensive began Thursday night, some 160 rockets have been fired, Israel’s military said, saying the number represented a “limited decline.”

“Not a big change, but the numbers are smaller than in the past couple of days,” said Capt. Eytan Buchman, an Israeli Army spokesman.

In southern Israel, though, a Hamas rocket killed a Bedouin man — the second Israeli civilian killed in the conflict — and badly injured an infant girl Saturday, said officials with Magen David Adom, Israel’s first aid agency. Twenty-nine people were slightly injured in the attack.

Sirens rang over communities in southern Israel all day.

During the ground offensive, Israeli troops have attacked more than 300 Hamas targets, including 112 command centers and 95 rocket launchers, the military said, and have found 13 tunnels from Gaza into Israel, with 31 openings.

In Gaza, evacuees watched from the top floor of an elementary school northeast of Khan Younis, one of the enclave’s hardest-hit areas, as round after round of Israeli tank and artillery shells fell a mile or two away.

Ten men gathered in front of a grocery store were killed before dawn when an Israeli missile struck the pavement. Small BB-size pieces of shrapnel flew from the explosion and flecked the walls with pinpoint holes.

The men’s funerals were sponsored by Hamas and Fatah, the other leading Palestinian party. Their bodies were draped in the flags of their movements, while religious and martial music blared.

Sanna Siri — whose sons Mohammad, 17, and Yahiva, 20, were killed — cried out to God and cursed the Israelis minutes after the funeral procession left her home.

“My sons went to the heavens as angels,” Siri said. She called the Israelis “pigs” and said she hoped they suffer.

Booth reported from Gaza City.