Unidentified assailants have sprayed the headquarters of one of the main political factions in Iran with automatic gunfire.

The office building on a busy street in central Tehran was full of party workers at the time as final preparations were underway for hotly-contested local elections throughout Iran on Friday.

According to eye-witnesses, two men on motorcycles drew up outside the building, fired some shots in the air then sprayed the front of the building with automatic gunfire, before escaping.

It is the first election since the Islamic revolution

The gunfire shattered windows, and the wall inside bore the scars of ricocheting bullets.

Nobody was hit directly by the shooting, though two women were taken to hospital suffering from cuts and shock.

The building was the headquarters of the "Executives of Construction". The party is the centrist political faction, which generally follows the pragmatic line of the former president, Hashemi Rafsanjani.

There was no immediate indication as to who carried out the attack or why, though the presumed intention of the provocation was to heighten tensions and undermine law and order.

One of the first to visit the scene was the Interior Minister Abdolvahed Musavi-Lari.