The defense establishment decided late Monday to close the border crossings between Israel and Gaza after Palestinian gunmen fired a Qassam rocket into the western Negev Monday afternoon in violation of a cease fire agreement between Israel and Hamas.

Two early warning "Color Red" sirens were heard in the Sha'ar Hanegev area and a rocket struck an open field shortly after. No injuries or damage were reported.

There was no immediate claim of responsibility for what was the fourth such attack since the Egypt-brokered truce went into effect on June 19.

On Sunday, Israel reopened three of its border crossings with the Gaza Strip after cross-border rocket fire stopped.

Israel had shut the crossings on June 25 after an Islamic Jihad rocket salvo which the Palestinian faction said was in retaliation for Israel's killing of one of its leaders in the West Bank.

Other Gaza militants have also fired a rocket and two mortar bombs in two separate incidents.

The Egyptian-brokered ceasefire requires militant groups to halt rocket fire in return for Israel gradually easing its blockade of the impoverished territory.

Israel sharply cut back the supply of goods into the Gaza Strip a year ago, after the Islamic militant group Hamas took over the territory from forces loyal to President Mahmoud Abbas's more secular Fatah faction.

Meanwhile Monday, the Knesset Foreign Affairs and Defense Committee approved the extension of a "special situation" declared in Sderot and other communities along the border with the Gaza Strip.

The special situation was declared in light of the ongoing Qassam and mortar shell fire from the Gaza Strip on Israeli communities.

The declaration essentially transfers emergency authority from the state to the army. Therefore, the Israel Defense Forces Southern Command can determine whether or not schools will remain open, and the Home Front can order factories containing dangerous materials to close their doors.