BAGHDAD, Iraq, Oct. 25 - Iraqi electoral officials announced today that a new constitution had been approved by voters, enshrining a legal foundation for the future governance of the country and paving the way for elections for a full-term government in December.

Seventy-nine percent of voters approved the constitution in the nationwide referendum held on Oct. 15, the officials said. But the vote was sharply divided along ethnic and sectarian lines. The biggest support came from Shiites and Kurds, who make up about 80 percent of the population, while Sunni Arabs largely rejected the document.

The constitution was widely expected to pass, but there was speculation until the very last minute that it may have been defeated by a three-province rejection. Under the electoral law, if two-thirds of voters in three provinces had turned down the constitution, the document would not have passed.

Officials said on Monday that two Sunni-dominated provinces had rejected the document; the results for a third province with a Sunni majority, Ninevah, were not released until today.

Officials said that, after an audit of the tally for Ninevah, they had determined that many people there had voted "no" on the constitution, but the number of rejections did not meet the two-thirds threshold.

The officials, at the suggestion of United Nations advisers, had also audited a random sampling of three provinces in which more than 90 percent of voters had approved the constitution. The officials said today that they had found no evidence of voter fraud in those provinces - Basra and Babil, dominated by Shiites; and Erbil, a Kurdish province in the north. The officials said it is standard international practice to scrutinize vote tallies when numbers are so heavily skewed in one direction.

Turnout among Sunni Arabs was high in the northern and eastern parts of the Sunni Triangle, a marked changed from last January, when Sunni Arabs largely boycotted elections for a transitional government. Their participation in the referendum has been hailed by American officials as a positive step, a sign that people opposed to the American enterprise here, including insurgents, may be co-opted through the political process. But the widespread rejection of the constitution among Sunni Arabs also shows a fierce hostility toward a document that was seen to be written by Shiite and Kurdish leaders.

The last-minute approval of the constitution by one Sunni Arab group, the Iraqi Islamic Party, seems to have done little to win support among voters for the document. That approval came after American officials helped negotiate a compromise that would allow the constitution to be amended in the first four months of the new Parliament, to be elected in mid-December.

With that in mind, Sunni Arab leaders are now calling for participation in the elections. They say they fear that the constitution will lead to the break-up of Iraq, because it allows regions to separate from the central government into virtually independent entities. The Shiites and Kurds, who each control oil-rich areas in the south and north, pushed hard for the right to create autonomous regions.

Sunni Arab leaders say they intend to win seats in the new Parliament and push through changes to the constitution that will water down those powers. An amendment must be approved by a simple majority of members of the new Parliament before being put to voters for a referendum.