At least two clusters of balloons carrying explosive devices that were apparently launched from the Gaza Strip landed in southern Israel on Thursday, with one of them detonating soon after impact, police said.

The balloon launches came after a day that saw tensions along the Gaza border spike suddenly, with rockets fired at Israel followed by reprisal strikes in the Strip.

One of the clusters landed in a open field and the other was tangled in a tree.

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Police sappers were called to the scenes in the Sdot Negev region east of Gaza.

One of the devices exploded as police sappers arrived at the scene. No injuries or damage was caused, police said.

The sappers collected the remains of the device in order to study what type of explosives were used, a police spokesperson said.

The tactic of launching balloons carrying explosive and arson devices from Gaza into Israel emerged in 2018 as part of a series of protests and riots along the Strip’s border, known collectively as the March of Return. The simple and cheap method of attack by Palestinians has proved effective as Israeli security forces have struggled to counter the tactic, but had largely stopped over half a year ago.

On Wednesday evening, police sappers were dispatched to the border town of Sderot where a suspicious object attached to a cluster of balloons landed in a residential neighborhood.

It appeared to mark the renewal of the arson balloon attacks that torched thousands of acres of Israeli fields along the Gaza border in recent years.

That incident came after terrorists — reportedly belonging to the Palestinian Islamic Jihad group — also on Wednesday fired four mortar shells from Gaza toward southern Israel, causing neither injury nor damage, according to the army.

Two of the incoming projectiles were intercepted by the military’s Iron Dome air defense system. The other two appeared to strike open fields in Israel’s Sha’ar Hanegev region, east of northern Gaza.

Hours later, the Israeli Air Force launched a series of strikes on Hamas sites in the Gaza Strip. According to the Israel Defense Forces, fighter jets attacked several Hamas facilities, including a weapons production site and a military base.

The mortar attack shattered a period of relative calm along the border.

It came three days since alarms last sounded in Nahal Oz, apparently due to heavy machine gun fire from the coastal enclave.

Israel has reportedly warned the Hamas and Islamic Jihad terror groups against any attempted response to the US targeted killing of Iranian general Qassem Soleimani earlier this month.

Hamas, which rules the Gaza Strip, expressed its “sincere condolences” to Iran’s leadership after Soleimani was killed in Baghdad on January 3 and hailed his support for the “Palestinian resistance,” but did not issue any overt threat.

The Islamist group’s leader in Gaza, Ismail Haniyeh, in the past lauded the “strong, powerful and warm” ties Hamas enjoyed with Soleimani, and spoke at the Iranian general’s funeral in Tehran.

The Iran-backed Islamic Jihad, which in November fought a two-day battle with Israel after one its military commanders was killed in an Israeli strike, has yet to respond.

Iran has for years sought to arm the Palestinian terror groups with rockets, mortars and missiles.

The US strike on Soleimani came amid efforts to broker a long-term ceasefire between Israel and Hamas, which have fought three wars since the terror group took control of Gaza in 2007.