The Israeli military says it struck a Hamas weapons manufacturing site and other targets in the Gaza Strip in retaliation for Palestinian militants firing a rocket into southern Israel early Saturday.
The escalation shatters a two-month lull in violence that prevailed along the Gaza-Israel fence in contrast to soaring tensions in the occupied West Bank.
A video showed the moment Israeli bombs targeted the Hamas site in the central Gaza Strip as plumes of smoke rose following loud explosions.
The military said another three Hamas posts were targeted but gave no other details.
Earlier on Saturday, Israel's aerial defence systems intercepted the projectile fired from Gaza, which activated warning sirens in the southern coastal city of Ashkelon. There were no reports of casualties.
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No Palestinian group claimed responsibility for the rocket fire. Israel usually blames the militant Hamas group for any violence emanating from the coastal enclave it controls.