An entrance to a tunnel that Israel’s military said it discovered just outside the southern Gaza Strip. (Amir Cohen/Reuters)

In the worst fighting in almost two years between Israel and Gaza Strip militants, repeated salvos of Palestinian mortar fire were met Friday by Israeli airstrikes deep in the coastal enclave as an escalation between the two sides reached a third worrisome day.

Both Israel and Hamas, the Palestinian Islamist militant movement, have said they want to maintain an Egyptian-brokered truce that ended 50 days of war in the summer of 2014 — an inconclusive fight that claimed the lives of 71 Israelis, mostly soldiers, and more than 2,100 Palestinians, including some 500 children and 250 women.

As each day passes, anxieties grow that a deadly rocket from Gaza or a devastating strike by Israel could set the stage for a fourth war between the belligerents.

The current round of fighting in Gaza began this week when Israeli troops entered the enclave and began to destroy offensive tunnels dug by Hamas along the Israeli periphery.

Hamas leader Ismail Haniyeh said Friday that his Gaza government does not want war but will fight Israeli incursions into the territory. Haniyeh said the Israeli troops penetrated a few hundred yards into a Gaza buffer zone in multiple locations.

Children sit in a window in the Shejaeiya neighborhood east of Gaza City near the border between the Gaza Strip and Israel on May 5. (Mohammed Saber/European Pressphoto Agency)

Using information that Israeli intelligence officers say they gleaned from a Hamas operative arrested last month, Israeli sappers and engineers, protected by ground troops and tanks, have been searching the border perimeter for attack tunnels since Tuesday.

Israeli Defense Minister Moshe Yaalon said that his troops will not be deterred by Hamas threats and will continue their search “until we find and expose every last tunnel.”

The back-and-forth comes as Prime Minister Benjamin Netanyahu faces a damning report by the state comptroller over his prosecution of the 2014 war with Hamas. The prime minister’s office said the report was political.

While Israeli troops have repeatedly ventured into the Gaza buffer zone over the past two years, their presence now has spurred them to action.

“The peace and quiet of the last two years has been a mirage, as both sides have spent the time preparing for the next war, when they should have spent the time securing a more lasting peace,” said Daniel Nisman, a security analyst for the Levantine Group.

The Israelis have to destroy tunnels that threaten them, and Hamas must respond when Israeli forces enter the strip, he said. Analysts call the Hamas mortar fire and Israeli airstrikes “rocket language” — meaning that it’s how Hamas, branded a terrorist group, and Israel talk to each other.

“Hamas can’t look gutless,” Nisman said. “They’re a resistance movement. That’s their whole point.”

Over the past three days, Israel says, Hamas has launched 12 salvos of mortar rounds against its forces operating along the perimeter fence. No Israeli soldiers or civilians have been hurt.

Gaza militias allied with Hamas, such as Islamic Jihad, are also alleged to have fired mortars, and their infrastructure — including a watchtower near the Gaza fence — has been hit by Israeli counterattacks.

Israel has responded to the harassing mortar fire with tank fire and F-16 airstrikes against multiple targets.

On Thursday, an Israeli missile killed a 53-year-old woman, Zeina al-Amour, in an attack near Khan Younis, according to the Palestinian Health Ministry. She was working on her farm when the missile struck, the Palestinians said. Israeli military spokesmen had no comment on the death.

The military wing of Hamas said two tunnels that Israeli for­ces found over the past three weeks were old excavations used during the 2014 war. Hamas said the Israeli government was looking for “false victories” and spreading lies to improve its image at home and abroad.

The Israel military says the tunnels were newly dug and designed for assault.

“Hamas’s diabolical plan to infiltrate into Israeli communities must be stopped,” said Lt. Col. Peter Lerner, an Israeli military spokesman.

Hazem Balousha in Gaza City contributed to this report.