GAZA CITY, Gaza Strip — Israel ordered the Gaza-Egypt border crossing closed just hours after it was partially opened for the first time in weeks. The crossing was to have been opened for two days to allow hundreds of people stuck in Gaza to leave after a weeks-long closure imposed during Israel’s military offensive in the coastal strip.

“We received a warning from the [Israeli army] that, for security reasons, the terminal will be closed. They were saying there were suicide bombers or something like that,” a spokeswoman for the European border monitoring mission, Maria Telleria, said.

The crossing had been opened to allow students, business people, and some people requiring medical treatment to travel to Egypt, Ms. Telleria said. About 500 sick people, many of them cancer patients, were given permission to cross the border for treatment, a Palestinian Authority official responsible for overseas medical treatment said.