GAZA CITY, Jan. 28 -- The radical Palestinian group Hamas, which has conducted numerous suicide bombings against Israelis and which the United States considers a terrorist organization, won an overwhelming victory in Thursday´s local elections in the Gaza Strip, capturing almost two-thirds of all the seats being contested and seizing power in seven of the 10 towns where elections were held, according to independent analyses of results released on Friday.

Hamas, known officially as the Islamic Resistance Movement, won 76 of the 118 total seats, dealing a staggering blow to the Fatah movement, which was founded by Yasser Arafat and has been the most powerful Palestinian party for more than 30 years. Fatah, which is also the party of the Palestinian Authority´s new president, Mahmoud Abbas, won 38 seats and took control of three councils. Three independent candidates and one from the radical Popular Front for the Liberation of Palestine also won seats.

Voter turnout was more than 80 percent.

Even though the Gaza Strip is Hamas´s home base, the results were striking, especially given that it was the first election for public office that Hamas had ever contested in Gaza and the voting took place in towns chosen by Fatah officials because they were assumed to be places where the party would do well. Fatah leaders were similarly stunned last month when Hamas won about 35 percent of the seats in 26 local elections in the West Bank.

"The magnitude was humongous. Many observers did not expect such a sweeping victory," said Hisham Ahmed, a political scientist at Bir Zeit University near Ramallah and an expert on Hamas. He said the results stemmed largely from widespread Palestinian disenchantment with Fatah and its corruption, the death of Arafat in November, and Israeli policies toward Palestinians that "are destroying secularism in Palestinian society."

Dore Gold, a senior adviser to Israeli Prime Minister Ariel Sharon who has written extensively on Islamic terrorism, said Hamas, aided by Saudi Arabia and Iran, has spent much of the last decade "creating a vast civilian infrastructure with schools, clinics, day care centers and a vast network of propaganda, and what you are seeing now is the fruits of that long effort."

Ahmed and Gold both said that the victory strengthened Hamas´s hand in negotiations with Abbas over power-sharing among the various Palestinian factions and a proposed cease-fire with Israel. The elections could also give Hamas tremendous momentum if it decides to field candidates in the parliamentary elections scheduled for July, they said.

Meanwhile, the warming trend between Israel and the Palestinians continued Friday, as hundreds of Palestinian security forces fanned out across the Gaza Strip to stop guerrillas from firing rocket and mortar rounds at Jewish settlements and Israeli towns. Israel´s military chief of staff, Lt. Gen. Moshe Yaalon, ordered Israeli troops to stop offensive actions in any areas in Gaza where Palestinian forces were deployed.

A statement by the Israeli military said that "in light of the ongoing cooperation," it would also scale back operations in the West Bank and would consider reopening three Gaza border crossings next week.

According to the statement, Yaalon also ordered that "targeting of terrorists in the West Bank will take place only if there is an immediate threat by active terrorist cells, and only with . . . explicit authorization."

Although candidates said that the elections had nothing to do with national politics and were strictly about the delivery of local services, much of Hamas´s campaign propaganda underscored its role in fighting Israel.

In the northern Gaza town of Beit Hanoun, which has been pummeled by the Israeli military in response to rocket fire, a large billboard showed a hooded Hamas militant on a knee, aiming a rocket-propelled grenade launcher on his shoulder. "The Qassam Brigades," the sign said, using the name of Hamas´s armed wing. "You see us in every field -- a lion that prevents the incursion."

In choosing the towns to be included in Thursday´s round of elections, Fatah officials had picked Beit Hanoun on the assumption that its residents would punish Hamas for inciting Israeli counterattacks. Instead, voters there gave 11 of 13 seats to Hamas, one to the Popular Front and one to an independent.

In Deir el-Balah, where a 70-foot-long banner pictured Sheik Ahmed Yassin and Abdel Aziz Rantisi, two Hamas leaders assassinated last spring by Israeli forces, Hamas won 13 of 15 council seats. "People in our town want services, and they see who has been working over the years," said Ahmed Kurd, 56, a local sheik and one of the Hamas members on the new Deir el-Balah council. "Our candidates have been involved in work for the community in schools, kindergartens and charity institutions, and now the public has come to pay its tribute. Researcher Samuel Sockol in Jerusalem contributed to this report. (© 2005 The Washington Post Company 01/29/05)