In a pre-dawn raid on Tuesday, IAF helicopters struck targets in Gaza, hitting two buildings associated with Al-Aksa Martyrs Brigades and roads believed to be used by Kassam crews to get to launch sites.
The strikes came the day after a Kassam landed near a kindergarten on a Negev kibbutz, narrowly missing children celebrating the Hanukka holiday, and another hit south of Ashkelon.
IAF missiles exploded in the Gaza Fatah offices and in a recruitment center operated by the organization in the town of Beit Lahiya.
No one was killed in the nighttime attack, and the military said it was deliberate.
"The targets were not people but infrastructure," an IDF spokeswoman said.
The IAF also hit six roads and a bridge near Beit Hanun, which the army said was used by rocket crews to reach Kassam launch sites.
Later, a jet bombed a road in northern Gaza.
"We are blocking access routes to the area," said Ra'anan Gissin, a senior adviser to the prime minister, adding that the establishment of a no-go zone would follow "should conditions worsen and Kassams continue to fall."
The Bush administration said Israel strikes in Gaza were a justified response to rocket attacks.
"What we would like to see is effective measures against such acts so that the measures Israel is taking are not necessary," US State Department spokesman Adam Ereli said.
In that vein, the spokesman said Maj.-Gen. Keith Dayton, the new US security specialist for the region, had arrived in the area for talks with Israeli and Palestinian Authority officials.
Speaking of Israel's rocket barrage, Ereli said: "We see it in the context of failure to address the security situation" by the Palestinians.
Lt.-Col. (res.) Moshe Mazuz, a researcher at the Interdisciplinary Center in Herzliya, said that government is giving the Palestinian Authority one last chance to put its house in order and stop the rocket attacks.
"Israel is just thinking aloud with this plan," said Mazuz.
B'Tselem spokeswoman Sarit Michaeli said that firing the inaccurate Kassams constitutes a "war crime," and Israel may warn Palestinians to keep away from rocket crews.
However, doing so did not absolve the military of having to distinguish between civilians and combatants, she said.
"Also, if Israel claims that Gaza is no longer occupied, it has no right to create nogo zones," said Michaeli. "It's on par with trying to create no-go zones in Jordan."
Meanwhile, security forces arrested seven Palestinians in the West Bank Monday night.
Paratroopers arrested two wanted men south of Nablus. During the operation, Palestinians threw a Molotov cocktail at an army jeep, damaging the vehicle and lightly wounding an officer inside.
In the city itself, troops picked up a member of the Popular Front for the Liberation of Palestine and another suspect carrying a rifle, two loaded magazines and a bag of bullets.
Soldiers of the Nahal infantry brigade arrested three Hamas terrorists in Hebron.
Finally, in Hadera, thieves found an old, quarter-ton air force bomb 100 meters from a residential area. Sappers destroyed the bomb.
In the evening, Palestinians fired on an Israeli car on Route 60, south of Nablus.
The driver escaped unharmed, but a Motolov cocktail was thrown at an IDF unit that arrived on the scene. There were no casualties.