The Palestinians' ruling Fatah movement won a majority on 51 municipal councils in elections held Thursday in 104 West Bank towns and villages, according to official results scheduled to be released Saturday that show the rival Hamas movement taking clear control of 13 councils.

Thursday's vote was the third round of municipal elections in the Palestinian territories. Voting in the Gaza Strip, where Israel recently ended its 38-year presence, was postponed to give election officials more time to prepare ballots.

In total, Fatah won 54 percent of the municipal seats, while Hamas, formally known as the Islamic Resistance Movement, won 26 percent. The remaining seats were won by several smaller secular parties and independent candidates, leaving 40 councils without a clear majority party. Fatah and Hamas could increase the number of councils in their control by forming coalitions with the smaller parties in the weeks ahead.

"Fatah faced the challenge of either leading as a secular movement or being defeated by an extremist religious party," said Shukri Radaideh, 45, a Fatah leader in the Bethlehem region. "The threat from Hamas made the party work better during this campaign, as Fatah had to choose between internal strife or facing this challenge."

The election took place as the Israeli military continued an intensive operation in the West Bank, sparked by a spate of recent rocket attacks from Gaza into southern Israel. Hamas, which refuses to recognize Israel, was behind a barrage of rocket fire that injured at least five Israelis last week.

The Israeli military responded with five days of airstrikes and selective artillery fire into Gaza, as well as mass arrests in the West Bank. Military officials said 441 Palestinians, most of them members of Hamas and the smaller radical faction Islamic Jihad, have been detained in the operation.

Political analysts said the arrests, which included some Hamas council candidates, likely undermined the group's showing at the polls.

In a statement posted on its official Web site, Hamas said that arrests were designed to "weaken the movement in the elections."

"The third round of elections are coming in the shadow of an onslaught against the Islamic Resistance Movement," the statement said. "This is an attempt to influence the results of the elections and the positions of the voters."

The next round of voting is scheduled for December. Palestinians in major cities in the West Bank and Gaza Strip will vote in that round, the last before parliamentary elections scheduled for January.

Hamas, which the Israeli government has demanded disarm before participating in those national elections, has broader appeal in poor urban areas where its extensive social programs and militant stand against Israel's occupation of land envisioned as part of a future Palestinian state are popular with refugees.

Staff researcher Samuel Sockol contributed to this report.