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Israel declared a “state of alert for war” on Saturday after Hamas launched its biggest attack on the country for years, firing a barrage of rockets and sending militants across the border from the Gaza Strip.

Mohammed Deif, the leader of Hamas’s military wing, said the Palestinian militant group had fired more than 5,000 rockets at Israel and called on Palestinians and other Arab states to join the fighting.

Israel’s military said that militants had entered Israeli territory “in a number of different locations”. The military closed roads around Gaza, ordering people near the coastal enclave to stay inside their shelters.

The escalation is the most serious bout of violence between the two sides since Israel and Hamas fought an 11-day war in 2021, and follows weeks of tensions on the border of Gaza, which has been blockaded by Israel and Egypt since Hamas took control of the territory in 2007.

“[Hamas] will face the consequences and responsibility for these events,” the military said. Rear Admiral Daniel Hagari, the spokesman for Israel’s military, said that it was attacking Hamas targets in Gaza.

Israeli paramedics said that one woman had been killed by a direct rocket hit and that a further 15 people had been injured, including two seriously. There was no immediate information about casualties in Gaza.

Israeli media reported that gun battles hads erupted between militants and Israeli forces in several locations in the south of the country while Palestinian media said that militants had taken some Israelis hostage.

An Israeli police spokesman did not immediately respond to a request for comment. An army spokesman had no immediate comment on the reports of hostage taking.

The rocket fire from Gaza set off warning sirens across the south and centre of Israel, with missiles targeting cities including Tel Aviv and Ashkelon, and the thud of interceptions heard as far north as Jerusalem, a city rarely targeted by missiles from Gaza.

Islamic Jihad, a smaller militant group based in Gaza, said that it had also joined the fighting.

The prime minister’s office said that Benjamin Netanyahu was on his way to the defence ministry to carry out a security assessment with the heads of the Israeli security establishment, while Israel’s defence ministry said that it had approved the call up of reservists.

The burst of fighting caps 18 months of simmering Israeli-Palestinian tensions, with outbreaks of violence in both Gaza and the West Bank, which Palestinians seek as the heart of a future state but which Israel has occupied since 1967.

According to the latest UN data, which does not include the latest violence, Israeli forces have killed 212 Palestinians this year, while Palestinians have killed 30 Israelis.