The Israeli army says its soldiers are withdrawing from the outskirts of Gaza City, where they have been operating for the past six days.

The army says searches in the Shejaiya area have revealed explosives caches and a 150-meter long underground tunnel leading to the Karni crossing point into Israel.

Palestinian witnesses and medics say at least 18 people -- including several civilians -- have been killed in Israeli air strikes, artillery fire and gunbattles since Israeli forces entered the area Saturday.

In the West Bank, Palestinians say Israeli troops killed a commander of the Palestinian al-Aqsa Martyrs Brigades militant group and wounded four other gunmen during a brief firefight in the city of Nablus early Thursday.

On Wednesday, U.N. Secretary-General Kofi Annan called for an end to Israel's offensive in the Gaza Strip, which began in late June. He also called on Palestinian militants to stop rocket attacks into Israel.

Mr. Annan spoke after meeting with Palestinian President Mahmoud Abbas in the West Bank town of Ramallah.

Israeli forces began their Gaza offensive to stop daily rocket attacks into Israel and to free an Israeli soldier captured by militant groups.

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