The celebration of Chaharshanbe Soori, Red Wednesday, on the evening March 16 marks the last Wednesday of the Iranian year and is rooted in pre-Islamic Zoroastrian tradition as a rite of the arrival of spring and is thus rejected by the country's ruling Muslim clerics.

Pro-Green Movement websites are recommending innovative methods such as "a Green silence - every Iranian should hold a candle and cry out loud, 'God is Great', and plant a tree", instead of taking part in violence and conflict with the authorities.

Police say they have confiscated more than 30 tonnes of explosives in Tehran alone and seven people have been killed across the country while making firecrackers and other devices. According to the news agency ISNA, 2,000 people were arrested last year.