The triumph by the Islamic militant group plunged the future of Mideast peacemaking into turmoil, with Israel saying it would not negotiate with a Palestinian government that includes members of Hamas.
Palestinian leaders, stunned by the militant group's sweeping victory, huddled to determine the shape of a new government as world leaders, including President Bush, insisted Hamas renounce violence and recognize Israel's right to exist.
It's the first time ever that militant Islamists have to come into power peacefully, in a democratic election considered free and fair by international observers, reports CBS News correspondent David Hakwins.
"I think it's almost a miracle the Palestinians were able to pull this off," Former President Jimmy Carter said.
Supporters of the two main parties briefly scuffled in Ramallah after Hamas supporters raised their party's green flag over the parliament. The two sides threw stones at each other, breaking windows in the building, as a small group of Fatah supporters tried to lower the banner. The crowd of about 3,000 Hamas backers cheered and whistled as activists on the roof raised the flag again.
Hamas won 76 seats in the 132-member parliament, while Fatah, which controlled Palestinian politics for four decades, won 43 seats, said Hanna Nasser, head of the Central Election commission. The 13 remaining seats went to several smaller parties and independents.
The result was based on a count of 95 percent of the vote and still could change slightly, Nasser said.
Hamas won 60.3 percent of the vote, said Ismail Haniyeh, one of the group's leaders.
In his first remarks since the election, acting Israeli Prime Minister Ehud Olmert said Israel won't negotiate with a Palestinian government that includes Hamas members.
"The state of Israel will not negotiate with a Palestinian administration if even part of it is an armed terrorist organization calling for the destruction of the state of Israel," said Olmert's statement, issued after a three-hour emergency Cabinet meeting.
Other Israeli politicians from across the political spectrum said there could be no relations with a group that has been responsible for scores of deadly attacks against Israelis and is listed as a terror organization by the United States and the European Union.