Israel's defense ministry has closed all border crossings with the Hamas-controlled Gaza Strip, following a suspected militant rocket attack from the area into Israel Thursday.
Israeli officials did not say when they would reopen the border.
No one immediately claimed responsibility for the attack. There were no casualties.
Israel imposed sanctions on Gaza after Hamas seized control of the territory last year.
A recent truce agreement requires Israeli authorities to gradually allow more goods into Gaza if militants there stop attacking Israel.
On Wednesday, a boat carrying international activists docked in the Gaza Strip with a delivery of humanitarian aid, in a move designed to call attention to Israel's blockade of the Palestinian territory.
Israel had said it would block the boat from landing, but its ships did not interfere.
Organizers with the "Free Gaza" campaign expressed hope that a regular ferry service could be established to deliver supplies to the Palestinians.
It is the second such journey that the U.S.-based "Free Gaza" group has carried out since late August. In the first incident, Israeli authorities allowed two boats to deliver humanitarian aid.
Some information for this report was provided by AP and Reuters.