The official said they had acted on information provided by Israel's internal security service.
Israel also pounded Gaza on Thursday, killing seven people days after a suicide bombing claimed by the Strip's Hamas rulers.
Saturday's death brings to 6,130 the number of people killed since the start of the second Palestinian uprising in 2000, the vast majority of them Palestinians, according to an AFP count.
Earlier on Saturday, an eight-year-old boy was seriously wounded when a rocket fired from the Gaza Strip landed in the southern Israeli town of Sderot.
The boy's 19-year-old brother was also wounded in the attack.
|Two Israelis were wounded by a Palestinian rocket fired from Gaza [AFP]|
"The child was walking in the street when the rocket fell," Micky Rosenfeld, a police spokesman, said.
The Ezzedine al-Qassam Brigades said it carried out the attack that wounded the boy.
Twelve Israelis have been killed by the rockets in the past six years.'Resolute measures'
David Baker, Israeli government spokesman, said: "Israel will take resolute and decisive measures to protect our citizens.
"We will not allow Israeli families to be victimised by Palestinian rockets in the heart of their own cities."
Israel imposed a blockade on the Gaza Strip, cutting supplies of food and fuel to the territory, in an attempt to get the residents to push for an end to the rocket attacks.
Several countries and human rights groups have condemned the move as "collective punishment".