Three people were wounded early Sunday morning in an Israeli air strike on Gaza, medical sources said, hours after another strike injured one man.
According to the sources, the latest air strike, which targeted a home in the al-Tufah neighbourhood in Gaza City, left the three in moderate condition.
The earlier strike, which took place late Saturday night, targeted a workshop in the Gaza City neighbourhood of Zeitun. The medical sources said all four casualties were civilians.
The Israeli army confirmed the attacks, with a spokeswoman telling AFP its aircraft "targeted a terror activity site and weapons manufacturing site in the northern Gaza Strip in response to the rockets fired at Israel."
"Direct hits were confirmed on both targets," she said.
Earlier in the day, the military said that four rockets had hit southern Israel over the past two days, including one Grad that struck south of Beersheba on Saturday. None of the rockets caused casualties or damage.
In addition, a rocket fired at Israel on Saturday by Palestinian militants hit a house in the Gaza Strip, but there were no casualties, witnesses in Gaza said.
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It apparently exploded prematurely, damaging the house, the witnesses said, without being able to provide further details.
In another incident, the military said an anti-tank rocket was fired at Israeli soldiers on Friday evening, but damaged the security fence separating Gaza from Israel.
Troops who responded with tank fire also neutralised an explosive device at the scene.
Since the beginning of the year, Palestinian militants in Hamas-controlled Gaza have fired more than 30 rockets at southern Israel, army statistics show.
Hamas has maintained a tacit truce with Israel, but other armed groups regularly fire rockets across the border, usually sparking retaliatory air strikes.
The Israeli army chief of staff warned in an interview broadcast Saturday night that increased rocket fire from the Gaza Strip will force Israel into "action."
"If this reality continues, and these launches continue and result in severe outcomes, we will have to take action, and we are ready for that moment," Lieutenant General Benny Gantz told the privately owned Channel 2 station.
Some 1,400 Palestinians and 13 Israelis were killed during a three-week Israeli offensive in December 2008 and January 2009 which was aimed at halting Palestinian rocket attacks.