They cut the main Gaza highway in several places, dividing the strip into northern, central and southern sectors.
The Israeli military says it has killed 130 militants over the past two days, greatly reducing rocket fire into the Jewish state.
Israeli Prime Minister Ehud Olmert says his country would not compromise on security. He said a ceasefire would be agreed to only if guaranteed an end both to attacks on Israel, and to Hamas rearming and rebuilding.
He added that he was contacting the leaders of several countries to pursue a diplomatic solution to the violence.
Ehud Olmert, Israeli Prime Minister, said, "About security, I am not compromising. Not here and not anywhere else. And I really hope that no one would be mistaken with any kind of illusion as for the level of our determination in every region and every front. We are not eager for any confrontation, we are not deterred by any threat."
At least 15 rockets were fired on Tuesday by Hamas militants. One landed in the town of Gadera, about 40 kilometers from the Gaza border, lightly wounding a 3-month-old infant. It's the farthest Israeli town to be hit by rocket fire so far.
UN officials say more than 540 Palestinians have been killed in Gaza so far, including more than 100 civilians.
Meanwhile, nine Israelis, including 6 soldiers, have died since the offensive began.
(CCTV January 7, 2009)
