The Israeli military has closed the border crossings into the Gaza Strip, after a rocket was fired from the Hamas-controlled territory into southern Israel.

An Israeli army spokesman says the rocket landed near the southern Israeli town of Sderot Thursday.  There were no reports of casualties, and no immediate claim of responsibility for the rocket launch.

Several rockets have been fired at Israel from Gaza, straining a fragile cease-fire deal between Israel and the territory's Hamas rulers that went into effect two weeks ago.

Gaza's Hamas leaders have warned militant factions in the coastal territory that it will take action against anyone violating the truce.  

Israeli Prime Minister Ehud Olmert also has warned that Israel will respond militarily if Palestinian militants continue attacks from Gaza in violation of the Egyptian-brokered truce.

Israel has responded to previous rocket fire by closing the border crossings used to bring supplies into the Gaza Strip.  Israel re-opened the crossings Wednesday to allow cement shipments into Gaza.

The border crossings were closed earlier this week in response to a rocket attack on southern Israel Monday.  There were no casualties in that incident.

Mr. Olmert has warned that Israel's restraint in the face of rocket attacks up to now should not be interpreted as a weakness.

Some information for this report was provided by AFP and Reuters.