News reports said dozens of rockets were fired into Israel from the blockaded Gaza Strip, and sirens warning of fire could be heard as far away as the Tel Aviv area.
The rocket fire began at 6:30 a.m. local time (03:30 GMT) on Saturday at several locations in the Gaza Strip and lasted for nearly half an hour, Agence France-Presse news agency reported.
Air raid sirens could be heard as far away as Tel Aviv, about 70 km (40 miles) north, and Israelis were ordered to stay in their homes and apartment buildings near bomb shelters.
Israeli rescue agency Magen David Adom 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 fragments, it was said.
Gaza residents said they also heard armed clashes along the separation fence with Israel near the southern town of Khan Younis and saw significant movements of armed Palestinian fighters. There were no further details from the Israeli military.
Israeli Prime Minister Benjamin Netanyahu’s office said he would meet with senior security officials in the coming hours.
There was no immediate claim of responsibility from Hamas, the armed movement that controls the Gaza Strip, nor from the smaller Islamic Jihad movement, which has also fought several wars with Israel.
The Israeli military had not yet commented, but its forces typically carry out airstrikes in response to rocket fire, raising the likelihood of major fighting.
The rocket fired on Saturday came after weeks of growing tensions along Israel’s volatile border with Gaza and clashes in the Israeli-occupied West Bank, where about 200 Palestinians have been killed by the Israeli military so far this year.
Around 30 people have died in Palestinian attacks on Israelis this year.
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