With 10,234,431 ballot papers counted, Ahmadinejad received 7,027,919 votes, or 68.88 per cent of the total. That compared with 2,955,131, or 28.87 per cent for his closest challenger, former premier Mir Hossein Mousavi, said Kamran Daneshjoo, chairman of the electoral commission at the interior ministry.
Former Revolutionary Guards commander Mohsen Rezai remained a distant third, with 162,909 votes, or 1.72 per cent. Ex-parliament speaker Mehdi Karroubi remained in fourth place with 88,474 votes, or 0.86 per cent.
Daneshjoo did not indicate where the votes were from, saying only that the counting was from polling places across the country.
Separately, a former senior member of the National Security Council, Agha Mohammadi, said Ahmadinejad was likely to end the day with a narrow victory, avoiding the need for a runoff.
"According to the information we have the voter participation will be 70 per cent overall and Ahmadinejad will have a little more than 50 per cent of the total vote," Mohammadi said.