JERUSALEM (AP) — Palestinian militants in the Gaza Strip carried out an unprecedented infiltration Saturday into southern Israel and fired thousands of rockets into the country as the ruling Hamas militant group announced the beginning of a new operation.

Israel began striking targets in Gaza in response, setting the stage for what was likely to be a new heavy round of fighting between the bitter enemies.

Videos posted on social media showed what appeared to be uniformed Palestinian gunmen inside the Israeli border town of Sderot. A video from Gaza showed what looked like the lifeless body of an Israeli soldier being trampled by an angry crowd shouting “God is Great.” Another video appeared to show Palestinian militants dragging away a live Israeli soldier on a motorcycle. Other videos showed a crowd of Palestinian men dancing around and atop an Israeli tank that was on fire. The authenticity of the videos could not immediately be verified.

The elusive leader of Hamas’ military wing, Mohammed Deif, announced the beginning of what he called “Operation Al-Aqsa Storm.”

“Enough is enough,” he said in the recorded message, as he called on Palestinians to join the fight. He said Hamas had fired over 5,000 rockets into Israel.

Salah Arouri, an exiled Hamas leader, said the operation was a response “to the crimes of the occupation.” He said fighters were defending the Al-Aqsa Mosque in Jerusalem and the thousands of Palestinian prisoners held by Israel.

The Israeli military confirmed an infiltration had occurred in several locations near the Gaza border in southern Israel. It ordered residents to remain indoors.

“The military declares a state of war alert,” it said in a statement. “In the last hour, the Hamas terrorist organization had begun a massive shooting of rockets from the Gaza Strip into Israeli territory, and terrorists infiltrated into Israeli territory in a number of different locations.”

It said Hamas “will face the consequences and responsibility.” Prime Minister Benjamin Netanyahu and top security officials were convening for an emergency meeting.

Israel has built a massive fence along the Gaza border meant to prevent infiltrations. It goes deep underground and is equipped with cameras, high-tech sensors and sensitive listening technology. The infiltration marked a major accomplishment — and escalation — by Hamas.

The sound of outgoing rockets whooshing through the air could be heard in Gaza and sirens wailed as far away as Tel Aviv and Jerusalem during an early morning barrage that lasted for over two hours. Israel’s Magen David Adom rescue agency said a 70-year-old woman was critically injured when a rocket hit a building in southern Israel. Elsewhere, a 20-year-old man was moderately injured by rocket shrapnel, it said.

As the rocket attacks continued throughout southern and central Israel, millions of Israelis were instructed to stay near bomb shelters in their homes and apartment buildings. The army said residents next to Gaza should stay in their homes due to the “security incident.”

The launches came after weeks of heightened tensions along Israel’s volatile border with Gaza, and heavy fighting in the Israeli-occupied West Bank.

Israel has maintained a blockade over Gaza since Hamas, an Islamic militant group that opposes Israel, seized control of the territory in 2007. The bitter enemies have fought four wars since then. There have also been numerous rounds of smaller fighting between Israel and Hamas and other smaller militant groups based in Gaza.

The blockade, which restricts the movement of people and goods in and out of Gaza, has devastated the territory’s economy. Israel says the blockade is needed to keep militant groups from building up their arsenals. The Palestinians say the closure amounts to collective punishment.

The rocket fire comes during a period of heavy fighting in the West Bank, where nearly 200 Palestinians have been killed in Israeli military raids this year. Israel says the raids are aimed at militants, but stone-throwing protesters and people uninvolved in the violence have also been killed. Palestinian attacks on Israeli targets have killed over 30 people.

The tensions have also spread to Gaza, where Hamas-linked activists held violent demonstrations along the Israeli border in recent weeks. Those demonstrations were halted in late September after international mediation.

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By JOSEF FEDERMAN and ISSAM ADWAN Associated Press