Israel is allowing hundreds of foreign passport holders to leave the Gaza Strip, where a seven-day offensive against Hamas has killed nearly 420 Palestinians and wounded nearly 2,000 others.

About 400 people are expected to evacuate Gaza Friday, raising speculation of a ground offensive by the thousands of Israeli troops massed along the border.

The Israeli army locked down the West Bank Friday for 48 hours, prohibiting movement into the occupied Palestinian territory except in emergency cases.

Israel also put thousands of security forces on alert, after Hamas urged Palestinians in the West Bank and Jerusalem to protest in a "day of wrath" following mid-day prayers.

Hamas vowed revenge after an Israeli air strike Thursday killed cleric Nizar Rayyan, the first senior leader of the Palestinian militant group to die in the offensive.

Despite Israel's bombing of key Hamas government buildings, smuggling tunnels and rocket launching sites, the Islamist militant group continues to fire rockets at Israel. Hamas attacks have killed four Israelis since Saturday.

World leaders concerned about civilians caught in the cross-fire are urging both Israel and Hamas to immediately stop their attacks.

The U.N. says at least a quarter of the Palestinians who have died were civilians, and that the survivors are in critical need of food.

Israeli Foreign Minister Tzipi Livni said Thursday in France that her country is distinguishing between Palestinian fighters and civilians, and that the humanitarian situation in Gaza is "completely as it should be.".

The Gaza Strip is a sliver of land along the Mediterranean Sea, about 10 kilometers wide and 40 kilometers long. One and a half million people live in the territory, making it is one of the most densely populated areas in the world.

Some information for this report was provided by AP, AFP and Reuters.