Palestinian militants fired hundreds of rockets from the Gaza Strip and Israel responded with airstrikes throughout Gaza. At least eight Palestinians and three Israelis have been killed in the violence.
The warning sirens signifying incoming missiles blared all day Saturday and into Sunday. Israelis living near the Gaza border have just 15 seconds to get to a bomb shelter. One of the Israelis was killed by a direct rocket hit on his home, and another when a rocket hit a factory in the southern Israeli town of Ashkelon.
Israel responded with dozens of airstrikes on Gaza, hitting both Hamas and Islamic Jihad targets.
Although Israel says Islamic Jihad fired the rockets, it holds Hamas, which controls Gaza, responsible.
Israeli Prime Minister Benjamin Netanyahu has ordered extra forces to the border with Gaza in preparation for a possible ground incursion.
Israeli analyst Neri Zibler told I24 News that Netanyahu does not want a war with Hamas.
"The greater good is to avoid needless wars. A war that you get into, you do not know how you will get out of it. A war that you go into and will most likely reach a conclusion and bring us back to the exact point we are in at the moment," he said.
The flare-up comes as Hamas and Islamic Jihad leaders are in Cairo trying to finalize a fragile agreement that was hoped to lead to a long-term cease-fire in Gaza.
The latest violent outbreak, the most intense along the Gaza in weeks, also comes days before Muslims begin the holy month of Ramadan and Israelis celebrate Independence Day.
The Eurovision song contest is also to be held in Israel at the middle of the month.