State television quoted Ayatollah Ali Khamenei directing a high-level clerical panel, the Guardian Council, to look into charges by pro-reform candidate Mir Hossein Mousavi, who has said he is the rightful winner of Friday’s presidential election.

The decision comes after Mousavi wrote a letter appealing to the Guardian Council and met Sunday with Khamenei, who holds almost limitless power over Iranian affairs. Such an election probe by the 12-member council is uncharted territory and it not immediately clear how it would proceed or how long it would take.