The Hamas militant group won local elections in the West Bank's largest cities, according to preliminary results released Friday, dealing a harsh blow to the ruling Fatah party just six weeks ahead of a parliamentary poll.

Hamas swept more than 70 percent of the vote in the West Bank city of Nablus, highlighting the fierce challenge posed by the group to Palestinian leader Mahmoud Abbas' Fatah party, which suffered a split Thursday when a group of young leaders broke away.

Meanwhile, Palestinian militants fired on an Israeli vehicle near the West Bank city of Hebron, seriously wounding a passenger, the army and rescue services said. The army sealed off the area after the drive-by shooting.

Early Friday, Israeli aircraft fired missiles at northern Gaza, wounding two Palestinians, residents said. The military said the targets were access routes to areas where militants launch rockets. At least six rockets landed in Israel on Thursday, one near the coastal city of Ashkelon. No injuries were reported.

The Israeli military on Thursday also imposed a closure on the West Bank and Gaza, barring all Palestinians from entering Israel, after troops discovered a car bomb near the West Bank town of Bethlehem. The bomb was detonated in a controlled explosion.

A Hamas victory in the Jan. 25 parliamentary poll could torpedo efforts to renew long-stalled Israeli-Palestinian peace talks, and damage the Palestinians' relationship with the United States. Hamas is sworn to the destruction of Israel and responsible for dozens of suicide bombings. The group is on the U.S. list of terrorist organizations.

"If the Hamas was ever to become a dominant force in Palestinian politics, that would be the end of the peace process," said Israeli Foreign Ministry spokesman Mark Regev.

Hamas' welfare programs, coupled with its fierce resistance to Israel's occupation, have won it grass-roots support among Palestinians who are fed up with Fatah's corrupt government and its inability to rein in lawlessness in the West Bank and Gaza Strip.

Abbas, meanwhile, is mired in an internal Fatah struggle. His last-minute attempt to unify the party's ranks failed Thursday when a group of popular young leaders split to form a new party called "Future," led by jailed uprising leader Marwan Barghouti.

Abbas had threatened to resign if Fatah fails to unite, according to participants of a party meeting. The seriousness of the threat was unclear, however.

Hamas' landslide victory is a direct result of Fatah's internal struggle, said Hani Masri, a Palestinian political commentator for the Al-Ayyam daily. He predicted a healthy showing for Hamas in the parliamentary vote.

"Fatah today is a sinking ship. Everyone is trying to jump ship and this will open the way for Hamas to win the upcoming election," Masri said.

In four of five rounds of municipal voting, Fatah has received 35 percent of council seats, compared to 23 percent for Hamas. However, Hamas has captured some of the Palestinians' largest cities, including Nablus, Qalqiliya and Jenin.

Thousands of jubilant Hamas supporters celebrated late Thursday in the streets of Nablus, where the group won 13 seats on the 15-member council. The two remaining seats went to a coalition of Fatah and independent candidates.

"The big party will be when we win the elections" for parliament, said Hamas spokesman Yasser Mansour.

In the town of Jenin, Hamas won eight seats, while a coalition between Fatah and the radical Popular Front for the Liberation of Palestine garnered seven. In el-Bireh, a large suburb of Ramallah, Hamas grabbed nine seats to Fatah's four. The PFLP and independents took the last two seats on the council.

Even in Ramallah, the West Bank's commercial hub and a city with a significant Christian population, Fatah only tied for first place, grabbing six seats in a coalition with other factions. The radical PFLP won another six seats, and Hamas won three. Official results will be announced Sunday.

Municipal voting in Hebron, the West Bank's largest town, was postponed until after the legislative elections in January because Fatah leaders feared that a Hamas victory there would fuel the militants' electoral momentum, a Palestinian official said on condition of anonymity because he was not authorized to speak on the subject.

Shimshon Arbel, Israel's former military governor in Nablus, said Hamas has invested a lot to build schools and clinics for ordinary Palestinians. Fatah, meanwhile, has been corrupt and failed to manage the Palestinian Authority, he added.

"The strengthening of Hamas is not a new phenomenon and not a new process," Arbel told Israel's Army Radio.