Traditional pre-Islamic celebration could be occasion for opposition protests.
Iranian officials are warning the opposition not to turn an ancient fire festival this week into a protest against the government.
The celebration of Chaharshanbe Soori, Red Wednesday, on the evening of 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.
But this will be the first time the occasion has been marked since last June's presidential election, which sparked a resurgence of opposition to the regime by the Green Movement that believes the poll was rigged.
The occasion has led to trouble and violence in the past because of rowdy behavior by young people and the use of illegal home-made fireworks, which have also caused injuries.
Police appear to be braced for a large number of arrests and young people are reported to be preparing home-made firecrackers and even grenades packed with gravel as they have done in recent years, which will fill the Tehran streets with explosions, smoke, and the smell of gunpowder. A black-market trade has grown up in the items, some of which are made by school children who get the information from the internet.
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.
This use of home-made explosives on Red Wednesday festival has evolved over the last decade as young people manifest their frustration over official restrictions imposed on social freedoms and popular entertainment.
Opposition leaders are encouraging people to protest peacefully. In a recent statement, one of them, Mir Hussein Mousavi, called for a "festival of light against darkness", which many saw as an invitation to protest this week.
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.
A member of Association of Social Psychology in Iran thinks the Green Movement will be revived on Chaharshanbe Soori after its failure to persuade people to protest on February 11, the anniversary of the Islamic Revolution. "I don't think it will be excessively violent, but clashes will certainly occur between the people and police," the person said.
The head of Tehran's fire department, Mohammad Reza Haji Beigi, was quoted as saying, "We certainly will have serious problems in this year's Chaharshanbe Soori. We need to have special planning."
Last year, the fire service reported 135 serious fires in Tehran alone on Red Wednesday.
Clinics and hospitals have put medical staff on call as they have done in the past.
He warned that as in previous years, the police will confront those who cause problems by blocking the streets or using explosives. According to the news agency ISNA, 2,000 people were arrested last year.
While some of the official precautions are ostensibly intended to make the event safe, members of the opposition believe they are also a warning against protests or disruption.
Since the Islamic Republic took power in 1979, Chaharshanbe Soori celebrations have gradually evolved into a struggle between the public and the authorities.
With joyous occasions frowned upon in Iran, the Islamist government has for years attempted to put a stop to this 4,000-year-old ceremony. It tried to replace national events in the Iranian calendar like Nowruz, New Year, which were regarded as originating in an "pre-Islamic age of ignorance," with those derived from the Islamic and Shia traditions,
Supreme Leader Ayatollah Ali Khamenei, in a recent posting on his official website, urged Iranians to avoid Chaharshanbe Soori celebrations as an "un-Islamic" event and other key figures within the religious hierarchy have also shown their opposition to the festival.
Ayatollah Makarem Shirazi was quoted as saying, "These festivities are not suitable for Muslims." Ayatollah Mohsen Mojtahed Shabestari, the supreme leader's representative in Tabriz, announced, "This festival is nothing but superstition."
Some believe President Mahmoud Ahmadinejad wants to eradicate the festival altogether. Tehran Governor Morteza Tamaddon, a close friend of Ahmadinejad, said on March 7, "With firm confrontation, we will try to erase the problem of Chaharshanbe Soori from people's minds in the next two years."
In the traditional Chaharshanbe Soori, Iranians would come onto the streets and build bonfires. Men and women would jump over fire and dance while chanting verses special to the occasion.
These lines reveal the cultural importance of fire in the Zoroastrian culture and seek to replace a person's problems and ill-health with warmth and energy.
The official rejection of Chaharshanbe Soori clashes with a natural desire of Iranian people to celebrate, leading to conflict with the police and turning what is meant to be a happy festival into a form of opposition.
A sociology professor at Georgetown University in Washington, Mehrdad Mashayekhi, believes violence by young people against the government is a psychological release, "When a government closes all the doors to its society, society finds ways to release its anger and frustration."
Sahar Sepehri is a journalist and media analyst based in Washington DC. This article was published by IWPR.