Iran’s presidential election was heading for a tense stand-off on Friday night as state news agencies declared Mahmoud Ahmadi-Nejad, the firebrand incumbent, had been re-elected with more than half the ballot, while his closest challenger alleged widespread fraud.

Mir-Hossein Moussavi, the moderate former prime minister, claimed he had actually won the election and appealed to Iran’s supreme leader, Ayatollah Ali Khamenei, “not to allow irregularities”.