The leader of Islamic militant group Hamas has announced the beginning of a new military operation against Israel, with a number of Palestinian militants infiltrating into Israel from the Gaza Strip.

In a rare public statement, Mohammed Deif said that 5,000 rockets had been fired into Israel early on Saturday to begin Operation Al-Aqsa Storm.

The Israeli military said “a number of terrorists have infiltrated into Israeli territory”, with residents along the border area ordered to remain indoors.

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The Israeli military usually carries out airstrikes in response to rocket fire (Tsafrir Abayov/AP)

The sound of outgoing rockets whooshing through the air could be heard in Gaza and sirens wailed as far away as Tel Aviv, some 70 kilometres (40 miles) to the north, during the early morning barrage that lasted more than 30 minutes.

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.

There was no immediate response from Israel. But the Israeli military usually carries out airstrikes in response to rocket fire, raising the likelihood of wider fighting.

Although there was no claim of responsibility for the rocket fire, Israel typically holds the ruling Hamas militant group responsible for any fire emanating from the territory.

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 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.