Iran's interior ministry said President Mahmoud Ahmadinejad moved into a strong lead Friday with nearly 70 percent of the votes tallied so far, but his pro-reform rival countered that he has clearly won and warned of possible vote fraud.
The dispute rose up even before polls closed early Saturday, heightening tensions across the capital where emotions have been running at a fever pitch. Mir Hossein Mousavi, the reformist candidate, suggested he might challenge the results.
The messy and tense outcome capped a long day of voting -- extended for six hours to accommodate a huge turnout. It raised worries that Iran's Islamic establishment could use its vast powers to pressure backers of Mousavi.
Voting in the Bay Area was called to a halt when officials in Emeryville ran out of ballots. More were being flown in from the East Coast. The polls were forced to shut down at 2 p.m. and were expected to reopen by 5 p.m. There is talk that the polls will remain open until midnight.
Hundreds of Iranians and Iranian-Americans turned out at Northern California's only polling place.
At times people had to stand in a long line along a corridor of the Hilton Garden Inn as they waited to enter the balloting room.
There were 41 voting sites in the the United States. Los Angeles is the next closest location to Emeryville.
During the voting, text messages were blocked -- a key campaign tool for reformers -- as well as some pro-Mousavi Web sites. Security officials warned they would not tolerate political gatherings or rallies before the final results were known.
Even before voting ended, Mousavi held a news conference to declare himself "definitely the winner" based on "all indications from all over Iran." But he gave nothing more to back up his claim and alleged widespread voting irregularities without giving specifics -- suggesting he was ready to challenge the final results.
Moments after Mousavi spoke, however, Iran's state news agency reported that Ahmadinejad was the victor. The report by the Islamic Republic News Agency also gave no details.
With more than 10 million votes counted, Ahmadinejad had 68.8 percent and Mousavi had 28.8 percent, said Kamran Daneshjoo, a senior officials with the Interior Ministry, which oversees the voting.
It was not reported whether the results were from locations considered Ahmadinejad strongholds or where Mousavi hoped to make headway.
The turnout was not immediately known, but election officials had predicted a possible record among the 46.2 million eligible voters. If true, that could make the 10 million votes in the neighborhood of 20 percent.
During the voting, some communications across Iran were disrupted -- Internet connections slowed dramatically in some spots, affecting the operations of news organizations including The Associated Press, and some pro-Mousavi Web sites were blocked. It was not clear what had caused the disruptions.
Text messaging was also cut off.
A high turnout was expected to help could help Mousavi, who is counting on an outpouring from what's been called his "green tsunami" -- the signature color of his campaign and the new banner for reformists seeking wider liberties at home and a gentler face for Iran abroad.
The president does not have the power to direct high-level policies, which are dictated solely by the ruling clerics. But the election focused on what the office can influence: boosting Iran's sinking economy, pressing for greater media and political freedoms, and being Iran's main envoy to the world.
Voters streamed to polling sites from the early morning until midnight -- with balloting extended by six hours. Some waited for hours in temperatures that hit 113 degrees in Iran's central desert or in nighttime downpours that lashed many parts of the country. In Tehran, a bride still in her wedding gown cast her ballot. Families making traditional Friday visits to relatives' graves filed into polling stations in the capital's sprawling cemetery.
Results are expected Saturday. But worries about the volatile atmosphere were already clear. The Interior Ministry -- which oversees voting -- said all rallies or political gatherings would be banned until after the formal announcement of results.
In Washington, President Barack Obama said the "robust debate" during the campaign suggests a possibility of change in Iran, which is under intense international pressure over its nuclear program.
"Ultimately the election is for the Iranians to decide," said Obama, who has offered to open dialogue with Iran's leaders after a nearly 30-year diplomatic freeze. "But ... you're seeing people looking at new possibilities. And whoever ends up winning the election in Iran, the fact that there's been a robust debate hopefully will help advance our ability to engage them in new ways."