JERUSALEM (AP) — Egyptian mediators rushed to the Gaza Strip on Wednesday and Hamas' supreme leader emerged from his hideout as an unofficial cease-fire between Israel and the Islamic militant group appeared to take hold.

The Egyptian delegation sought to cement the truce that ended two days of heavy fighting between the bitter enemies. They face a key test on Saturday, when Hamas is planning a mass demonstration to mark the one-year anniversary of weekly protests along the Israeli border.

In a sign that both sides had stepped back from a major conflagration, Hamas' supreme leader Ismail Haniy...