Terrorists in the Gaza Strip fired rockets at the city of Sderot and nearby communities on Monday night, some 20 minutes after a ceasefire was reportedly due to go into effect at 10 p.m.

There were no immediate reports of injuries or damage from the attack. Residents of the area reported seeing multiple Iron Dome interceptor missiles fired into the sky.

Over the course of Sunday and Monday, some 90 rockets were fired at Israel from the Gaza Strip — most of them by the Palestinian Islamic Jihad terror group — and approximately 90 percent of those heading toward populated areas were intercepted by the Iron Dome system, according to the Israel Defense Forces.

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In response to the attacks, the Israeli military launched multiple rounds of retaliatory air raids against Islamic Jihad bases in the Gaza Strip, as well as one airstrike on a squad it said was preparing to launch rockets, injuring four.

Just before the ceasefire was meant to begin, terrorists in the Strip also fired a number of rockets at the Eshkol region of southern Israel. One rocket struck inside a community in the region, causing no injuries, but light damage to a nearby building, which was hit by shrapnel.

In light of the ongoing attacks from Gaza, the military ordered schools to remain canceled Tuesday in Gaza periphery communities, including the city of Ashkelon, representing some 55,000 students.

In response to the rockets, Israel on Monday night announced it would close all border crossings between Gaza and Israel, with the exception of humanitarian cases, until further notice. Gaza’s fishing zone would also be completely shut down.

IDF Chief of Staff Aviv Kohavi warned Monday evening that the fighting may not be over yet.

“It’s unclear if the incident is at its peak or its end, if it will escalate or die down,” Kohavi said at an event for military reservists in the central city of Holon.

Kohavi said the situation was fragile and could unintentionally escalate to a full-blown conflict and an IDF operation.

He stressed: “I don’t think that’s where we’re going… but a not insignificant number of operations, even wars, in the past 20 years began like that — through escalation that developed into something much bigger.”

He vowed to “do everything to prevent [residents of the south] from feeling insecure and to protect them in every way we can.”

In a short statement, Islamic Jihad on Monday night said it had completed its “retaliation” for Israel’s killing of its three members on Sunday. But it said it would respond to any further Israeli “aggression.”

Palestinian terror groups said the ceasefire would come into effect at 10 p.m., the Gaza-based Dunya al-Watan news site reports, citing “well-placed sources.” Subsequent reports, citing Palestinian Jihad sources, said the ceasefire would take effect at 11:30 p.m.

An Israeli security official confirmed that Israel received “messages from various ranks within the Palestinian Islamic Jihad organization regarding a desire for an immediate ceasefire.”

The official, who spokes anonymously, said Israel was “skeptical” of the requests by the Islamic Jihad. “The IDF will continue to act until quiet is restored to the south,” the official said.

A source in Islamic Jihad also expressed skepticism as to whether the ceasefire would hold, telling Palestine Today, which is linked to the terror group: “The talk about setting specific times for a ceasefire is incorrect. It is dependent on the occupation halting its aggression.”

The group launched dozens of rockets at cities and communities throughout southern Israel on Monday. No physical injuries were reported in those bombardments, though some of the projectiles caused damage to homes and infrastructure. A small number of Israelis sustained minor injuries while running to bomb shelters.

Both Israeli and Palestinian officials threatened to step up their strikes if the other side continued its attacks.

Prime Minister Benjamin Netanyahu appeared to threaten to kill the heads of Gaza’s terror groups if rocket fire from the Strip continued.

“We will continue to strike until the calm returns. If there isn’t quiet, you’ll be next,” Netanyahu said, during a visit to the city of Ashdod.

The round of violence was sparked by an irregular clash along the Gaza border Sunday morning in which Israeli troops shot dead a member of Palestinian Islamic Jihad as he planted an improvised explosive device along the border. The Israeli military then retrieved his body, using a bulldozer.

The retrieval of the corpse was apparently part of Bennett’s announced plan to “hoard” the corpses of Palestinian terrorists in order to use them as “bargaining chips” in negotiations for the release of two Israeli men, and the remains of two fallen Israeli soldiers, who are being held by Hamas in the Gaza Strip.

On Sunday evening, Islamic Jihad and other terror groups fired some 30 rockets at Israel, approximately half of which were intercepted by the Iron Dome missile defense system. The rest landed in open fields. Some shrapnel caused light property damage, but no injuries were reported.

The IDF retaliated with airstrikes on Islamic Jihad facilities in both Syria and Gaza. Two members of the terror group were killed in the airstrikes outside Damascus along with four other pro-Iranian fighters, according to a Britain-based Syrian war monitor.

The border clashes come amid reports of ongoing efforts by Israel to seal a ceasefire agreement with Gaza terror groups, following weeks of intermittent rocket fire and the regular launching of balloon-borne explosive devices into Israel.

Adam Rasgon contributed to this report.