The state news agency IRNA has also declared Mr Ahmadinejad the "definite winner".

With 80 percent of the vote counted, Mr Ahmadinejad has 65 percent support and has claimed victory in an election that drew a large turnout.

His leading rival, reformist candidate Mir Hossein Mousavi has complained of a number of voting irregularities. The election commission says Mr Mousavi's share of the vote was around 32 percent.

Four candidates contested the election, with Mohsen Razai and Mehdi Karroubi only registering a small percentage of votes.

Iranian affairs analyst Sadeq Saba says the latest official results suggest Mr Ahmadinejad will be a clear winner in the first round as the pattern of voting is not expected to change.

A candidate must secure 50 percent in the first round to avoid a run-off vote.