The rocket attacks came after reports that Egypt had mediated a cease-fire with Hamas and other Palestinian factions in Gaza, Israeli television channels reported.
More than 110 rockets were fired at southern Israel Saturday night and Sunday, the army said.
One of the rockets hit the yard of a home in Netivot in southern Israel.
Twenty-six people in Netivot were treated for shock, Army Radio reported.
The Iron Dome missile defense system intercepted two of five rockets fired at Ashkelon, military officials said.
The Islamic Jihad and Popular Front for the Liberation of Palestine refused to accept the cease-fire and called for continued response to Israel's "aggression," the Palestinian news agency Ma'an said.
Israel, which had not officially commented on the reported truce, conducted three strikes on terrorist targets in northern Gaza early Monday, officials said.
Despite the rocket fire, a decision was made to reopen schools in the rocket-prone areas, Israeli media reported.
Israeli Prime Minister Binyamin Netanyahu was to meet in Jerusalem Monday with a group of 50 foreign diplomats to update them on the recent escalation in violence, his office said.