Israeli helicopters attacked a Hamas training field early Tuesday, killing at least 13 Palestinians and wounding 25 in the bloodiest strike in Gaza (search) in months, officials from both sides said. Most of the casualties were members of the anti-Israeli militant group.

The attack came a week after Hamas (search) carried out a double homicide bombing in the southern Israeli city of Beersheba, killing 16 Israelis and breaking a six-month lull in major violence against the Jewish state. The homicide bombers were from the West Bank city of Hebron.

The Israeli military said the air force targeted the field, near the border with Israel, that was being used by Hamas for bomb assembly and training.

Angry Hamas militants gathered at Shifa Hospital in Gaza City — some with blood on their clothes from carrying victims — shouting "revenge, revenge."

"This bloody crime is a new wave of aggression committed against our people and against our sons," Hamas spokesman Mushir al-Masri said. "It's an ongoing war. One day for us and one day for them."

The Israeli statement listed events that it said took place at the field in recent days, including assembly of a large bomb and a homicide bomber's vest, practice in hijacking vehicles and training in preparing and firing mortars and rockets.

Al-Masri denied that the targeted field was used for training, calling it a summer camp for Palestinian youth.

Hospital officials said at least 13 people were killed and 25 wounded. Witnesses said the casualties were members of the Hamas military wing or supporters. Many wore military-style uniforms.

The airstrike was in the Shajaiyeh section of Gaza City, a known stronghold of the violence Islamic Hamas. The casualty toll was the highest in Gaza City since May, when a spate of heavy fighting killed 31 Palestinians and 13 Israeli soldiers.

On Monday, Israel's defense minister Shaul Mofaz said he is moving another planned section of the West Bank (search) separation barrier closer to Israel. Israel says it needs the barrier to keep out homicide bombers.

The barrier is part of Prime Minister Ariel Sharon's contentious plan of "unilateral disengagement" from the Palestinians, including a withdrawal from the Gaza Strip and the evacuation of four small West Bank settlements in 2005. Sharon has said he wants to keep several large West Bank settlements as part of any future peace deal.

One-third of the 425-mile barrier has already been built in the northern West Bank, but army planners have redrawn parts of the remaining route further to the south to comply with the court order. Palestinians have complained that the wall's path in the north has cut off Palestinians from their land and other services.

Israel began construction of the southern segment of the barrier after Palestinian homicide bombers infiltrated across the unprotected line there and blew up two buses in Beersheba last Tuesday.

The original plan in the south was to cut into the West Bank in several places to include some Jewish settlements on the "Israeli" side, but Mofaz said Monday this was being changed.

"In light of the Supreme Court (rulings), we decided to plan another route that in principle ran along the Green Line," Mofaz told Army Radio, referring to Israel's old frontier, before it captured the West Bank in the 1967 Mideast war.

Jewish settlements that find themselves on the "Palestinian" side will be encircled by separate fences, Mofaz said.

Sharon reportedly wanted to include some of these settlements on the Israeli side. A Sharon adviser, Raanan Gissin, said no final decision has been made, but that he did not expect major changes to the route proposed by Mofaz.

The separation barrier has disrupted the lives of thousands of Palestinians, cutting them off from schools, jobs and land. Earlier this year, the Israeli Supreme Court ordered changes in the planned route to ease hardships.

Palestinians object to the barrier in principle, calling it an "apartheid wall" meant to dictate borders, effectively annexing parts of the West Bank to Israel.

The world court has issued an advisory ruling calling the barrier illegal, saying it should be torn down. Israel dismissed the ruling as one-sided and politically motivated, but Israel's attorney general has said the ruling can't be ignored, and the Supreme Court ordered the government to state how it is dealing with it.

Israel broke ground Sunday on a 25-mile stretch that officials said would run along the Green Line.

Mofaz on Monday referred to a separate 35-mile stretch, security officials said. The original route would have effectively annexed about 20 square miles of West Bank land.

Also Monday, visiting Egyptian officials told Palestinian leaders that they would not send experts to Gaza to help train Palestinian forces to take control there unless Israel accepts a cease-fire, a Palestinian official said.

Egyptian Foreign Minister Ahmed Aboul Gheit and intelligence chief Omar Suleiman met Palestinian leader Yasser Arafat to discuss cease-fire efforts and the planned Israeli pullout from Gaza.

Palestinian Foreign Minister Nabil Shaath told The Associated Press that the Egyptians called for Palestinian unity. Egypt has been trying unsuccessfully for more than a year to forge a common Palestinian declaration of a truce in the conflict with Israel.

Shaath said Egypt is calling a meeting at the end of the month with all the Palestinian factions to press the truce idea.

"Until Israel accepts a comprehensive cease fire, they will not send their experts to Gaza," Shaath said.

Israel has not been approached about a new cease-fire. Last summer Palestinians declared a unilateral truce, but it collapsed after a few weeks amid Palestinian attacks and Israeli retaliation.