JERUSALEM, July 3 (Xinhua) -- Israel closed its border crossings with the Gaza Strip again on Thursday following a rocket attack from the Hamas-ruled enclave, further straining the shaky truce.

    The rocket hit an open field near the border town of Sderot in the afternoon, causing no casualties, which is at least the fifth such attack since the Egypt-brokered truce went into effect on June 19.

    Following the latest violation, for which no group has claimed responsibility, Israeli Defense Minister Ehud Barak instructed the army to close all the border crossings with the Palestinian territories.

Palestinians wait in line for pure drinking water at a UN water station in the Gaza Strip July 3, 2008

    The move marks the third time that the Jewish state closes the border in response to rocket attacks from the Gaza Strip since the implementation of the ceasefire. The previous two closures last four days and one day respectively.

    It is still unknown when Israel will reopen the crossings to allow supplies into the largely blockaded area. Local daily The Jerusalem Post reported that the crossings will remain closed on Friday.

    Hamas has pledged to rein in other militant groups in the Gaza strip, calling on them to honor the ceasefire deal while vowing to punish those who violate it.