The border at Rafah, the only exit from the Gaza Strip that is not on the Israeli border, opened at 1.30pm on Tuesday. No date has been set for its closure, according to the Israeli news agency Mena.
Egypt usually keeps the border closed and is in the process of constructing a steel wall underground to prevent civilians from Gaza crossing into Egypt.
Gaza has been blockaded by Israel since the Islamist party Hamas took power in 2007.
Meanwhile, five Palestinians were killed Tuesday on the border between Israel and Gaza.
The Israeli army announced it had killed two armed men who had crossed the border from southern Gaza. The military said there was an exchange of fire, but no Israelis were injured.
The other three were killed by an Israeli strike in the north of the territory, according to Gaza emergency services.
The Israeli military said it carried out an air strike about an hour after two rockets were fired from Gaza. The Palestinian group Islamic Jihad claimed responsibility for the rocket attack.