Israel hits dozens of militant targets in Gaza as tensions intensify.

JERUSALEM • Israel warned it was closer to war in Gaza than it had been in years after Palestinian extremists fired dozens of mortars at Israeli towns.

Israel’s military responded with heavy airstrikes across Gaza.

“Israel will exact a heavy price from those who seek to harm it, and we see Hamas as responsible for preventing such attacks,” Prime Minister Benjamin Netanyahu said following the barrage.

In the most serious exchange of fire between the two sides since the end of the 2014 conflict, Israel’s military said waves of missiles were fired out of Gaza into southern Israel. At least three soldiers were wounded. One shell fell into the yard of a kindergarten, spraying the front of the school with shrapnel.

Israel accused the militant group Islamic Jihad of doing most of the shelling but said Hamas, the Islamist faction which controls Gaza, also participated in the attack. Israeli jets struck more than 30 Hamas and Islamic Jihad bases across Gaza in response, the military said. No injuries were reported in Gaza from the strikes.

The exchange of fire comes after weeks of heightened tensions on the Gaza border, where Israeli forces have killed more than 100 Palestinians during protests.

Although neither Israel nor the Palestinian factions are believed to be looking for a full blown war, the shooting raised concerns about an escalation of violence that could send both sides stumbling into all out conflict.

Israel Katz, the Israeli intelligence minister, said the country was closer to war with Hamas than it had been at any point since 2014. “We are the closest to the threshold of war since Operation Protective Edge,” he said. “We don’t want it, and the other side doesn’t either, but we have our red lines.”

The shelling from Gaza into Israel was widely condemned internationally and Britain said the “indiscriminate attacks” were “completely unacceptable under any circumstances.”

The mortar shells and rockets fell in and around Israeli communities near the Gaza border, triggering air raid sirens and sending thousands of Israelis running for bomb shelters. The Israeli military said many of the projectiles were intercepted by the Iron Dome missile defence system.

Video from the Israeli kindergarten showed the front of the building had been pockmarked by shrapnel from a mortar. The shell struck at around 7 a.m., before any children had arrived at the school. “Seven o’clock is the busiest time of day. This could have ended differently,” said Merav Cohen, an Israeli mother who lives near the kindergarten.

WE DON’T WANT IT ... BUT WE HAVE OUR RED LINES.