Israeli warplanes launched two new raids early on Wednesday on smuggling tunnels linking the Gaza Strip to Egypt without causing casualties, witnesses said.
An Israeli army spokesman confirmed the bombings, saying three tunnels had been attacked and "secondary explosions took place in one of them, indicating the presence of explosives."
On Tuesday, the airforce had carried out some seven raids wounding four people, following rocket fire from the Hamas-ruled territory, witnesses and medics said.
Palestinian witnesses said aircraft carried out at least seven strikes along Gaza's southern border, where dozens of tunnels are used for trafficking people, goods and arms into the impoverished territory.
Four people were wounded in the raids, Palestinian medics said.
An army spokeswoman told AFP that the air force carried out six strikes against smuggling tunnels near the southern Gaza town of Rafah "in response to barrages of rockets fired over the past week".
Outgoing Foreign Minister Tzipi Livni had earlier warned that Israel would not shy away from striking Gaza in response to persistent rocket fire.
"If it turns out that Hamas has not got the message, it will be hit again," Livni told public radio hours before meeting US Secretary of State Hillary Clinton on her first official visit to the Jewish state.
Late Tuesday Palestinians fired more rockets at southern Israel from the northern Gaza Strip, but nobody was hurt and no damage reported, an army spokesman said, adding that the rockets fell on wasteland south of the town of Ashkelon.
Some 120 rockets fired from the Palestinian coastal strip have been tallied since twin ceasefires came into force on January 18 following a three-week Israeli offensive which claimed more than 1,300 lives.