The Rafah crossing with Egypt was closed on Wednesday and part of Thursday after the Israeli army shut the nearby Kerem Shalom passage into southern Gaza over a security alert. Monitors use the passage to get to Rafah.
"We were informed late last night by the IDF [army] that the security state in Kerem Shalom does not allow for the gates to be opened for us to cross to the Rafah terminal. At the moment, the crossing is not open," a spokesman for the monitors said.
An Israeli army spokeswoman said the monitors could get to Rafah by entering through another crossing point. But the monitors say Rafah cannot reopen unless a liaison office at Kerem Shalom is functioning.
The Islamic group Hamas has said it suspected Rafah was closed to stop its government from carrying cash by hand into Gaza to sidestep a Western aid embargo. The monitors have denied the accusation.