Aljazeera's correspondent in Gaza reported that Israeli warplanes launched five air strikes inside the Gaza Strip in the early hours of Tuesday morning.
The first attack targeted an uninhabited area while the second hit an office of Fatah in the city of Bait Lahiya, north of the Gaza Strip, causing serious damage.
The third strike struck east of the Gaza Strip, the fourth targeted the northern Salah al-Din street while the fifth one hit the city of Bait Hanun causing infrastructural damage. No casualties were reported.
Hours later, about two dozen armed al-Aqsa fighters demanding jobs took over three buildings - the governor's office, the Education Ministry and a religious court, in northern Gaza.
The armed men entered the buildings in northern Gaza armed with hand grenades, RPGs, rocket launchers and automatic rifles. Police stationed in a building next door watched the men enter, witnesses said, and did nothing to prevent the takeover.
Later, security surrounded the governor's office and Fatah officials, mediating by phone, tried to persuade the armed men to leave.
Dozens of children from a nearby school milled around watching the action, while two Israeli helicopter gunships hovered overhead. Police tried to set up roadblocks and keep the crowds away.
The Israeli army said they launched the air strikes on Tuesday after a number of rockets were fired into Israel, causing no damage or injuries. The firing was reportedly claimed by the al-Aqsa Martyrs' Brigades.
Since Israel's withdrawal this summer from the Gaza Strip, more Israeli towns - including the city of Ashkelon and its power plant - have come into Palestinian rocket range. Earlier this month, a rocket landed near the power plant and a fuel depot, angering the Israelis.
Israeli Defence Minister Shaul Mofaz had on Monday ordered the army to begin implementing a security zone in the northern Gaza Strip that Palestinians will be barred from entering, a ministry source said.
Jobs in the Palestinian security
services are in high demand
The Israeli source said: "The defence minister has ordered the army to apply from Monday evening a decision taken last Thursday setting up a limitation on Palestinians circulating in the northern Gaza Strip, following rocket fire launched from this area toward southern Israel."
Israeli radio reported on Sunday that Ariel Sharon, the prime minister, had ordered the army to set a buffer zone in northern Gaza, a plan rejected outright by Palestinian leaders.
Any Palestinian straying into the zone, the extent of which will be determined by the Israeli occupation army, could be shot by troops from across the border.
Local media had reported that the army was awaiting an improvement in the weather before starting to enforce the area, but without re-occupying the territory it withdrew from earlier this year after a 38-year occupation.
Furthermore, Israel's Haaretz newspaper reported on Tuesday that the Israeli military intends to scatter warning notices from air force planes before striking Gaza Strip targets as it begins enforcing the buffer zone.
The notices will be scattered around areas from which Palestinian fighters launch Qassam rockets into Israel, Haaretz said.
The leaflets will call on Palestinian police officers to evacuate the northern Gaza Strip, and will state that the responsibility for potential civilian casualties in Israel air force strikes lies with the Qassam launchers, the newspaper added.
Also on Tuesday, dozens of armed men took over a West Bank office of the Palestinian election commission to protest over President Mahmoud Abbas's choice of candidates for an upcoming parliamentary election.
The armed men from al-Aqsa Martyrs Brigades, part of Abbas's Fatah movement, said they seized the al-Ram office to demand the inclusion of candidates representing neighbouring Jerusalem on the list of those contesting the 25 January vote.