Eighteen Palestinian civilians, including ten children who were members of an extended family, were killed early Wednesday, by Israeli shelling in the northern Gaza Strip. In the West Bank, Israeli troops killed four militants and one civilian in a fire fight near Jenin.  Israel's defense minister has ordered a temporary halt to all shelling in the Gaza Strip, pending an investigation into the incident.

A Palestinian man carries his injured daughter into the Beit Lahia hospital in the northern Gaza Strip, November 8, 2006

Palestinian witnesses say artillery shells struck several houses in Beit Hanoun in the pre-dawn hours, Wednesday. Hospital emergency rooms in Gaza City say more than 50 people were wounded in the attack - many of them women and children who were struck by the shells as they slept.

Palestinian Prime Minister Ismail Haniyeh, a leading Hamas militant, says three days of mourning have been declared. Palestinian security officials held emergency meetings to discuss the situation.

Haniyeh says talks on creating a unity government for the Palestinians should be suspended and he appealed to the Arab League and the United Nations to intervene, on behalf of Palestinians.

Speaking later, Palestinian President Mahmoud Abbas called the incident a massacre, but he says moves to form a unity government should proceed.

Israeli Prime Minister Ehud Olmert and Defense Minister Amir Peretz both expressed their condolences on Wednesday and said that Israel will supply emergency humanitarian aid to the Palestinian Authority.

Israeli troops withdrew from Beit Hanoun, Tuesday, after a week-long military operation in the town, designed to stop Palestinian militants from firing rockets at southern Israel. More than 50 Palestinians, mostly militants, were killed in the operation. One Israeli soldier was killed in the fighting.

Israel resumed artillery strikes on the town, late Tuesday, after Palestinian militants fired a barrage of rockets at the southern Israeli city, Ashkelon.

News reports say Israeli troops firing in response, missed their target, striking a compound of several buildings where the victims lived. Israeli officials are promising a thorough investigation of the incident.

"Every little detail will be investigated," said Jackie Eldan, the deputy spokesman for the Ministry of Foreign Affairs.  "The fact that it may have been an error has yet to be studied. It is too early and that has to be studied, it will take a few days, but I can promise you full transparency and as soon as we know what has happened we will let everybody know."

Wednesday's deaths have raised tensions in Gaza to a new level. The military wing of the Hamas militant movement has issued a statement calling on Muslims, around the world, to attack American targets. The United States, Israel and the European Union have classified Hamas as a terrorist group, and have cut all assistance to the Hamas-led Palestinian government.

Hamas and other Palestinian militant groups have also threatened to resume suicide attacks in Israel in response to Israel's military activities in Gaza.