Militants in the Gaza Strip have fired more than 200 rockets into Israel, the army says, prompting air strikes and tank fire on the Palestinian territory.
Three Israelis were wounded by the rockets. Israeli fire killed three Palestinians, including a mother and her baby daughter, Gaza officials say.
Four Palestinians, including two Hamas militants, were killed on Friday after an attack injured two Israeli soldiers.
The flare-up followed a truce in the run-up to Israeli elections in April.
It marks yet another increase in hostilities despite attempts by Egypt and the United Nations to broker a longer-term ceasefire.
The rocket barrage began at 10:00 (07:00 GMT) – and was still continuing some 12 hours later, the Israel Defence Forces (IDF) said.
Several homes in parts of Israel bordering the Gaza Strip have been hit. Many residents rushed to bomb shelters.
The injured include two men in Ashkelon, 10km (six miles) north of Gaza, and an elderly woman in Kiryat Gat, further east.
The country’s Iron Dome missile-defence system shot down dozens of the rockets, IDF said.