Which State Security Branch Rules Tehran's Streets?

Two weeks after the contested results of Iran's presidential elections led to widespread street riots and demonstrations across the country, the Islamic republic pronounced its harshest threat yet to protesters. At the official ceremony for Friday prayers, Ayatullah Ahmad Khatami, a hard-line cleric who often delivers the sermon, said those who agitate on the streets were "waging war against God," a crime that carries the death sentence.

It was the latest example of government forces tightening their control over and heightening their rhetoric against opposition supporters of the defeated presidential candidate Mir-Hossein Mousavi. Demonstrations and rallies have ground to a halt as the heavy presence of police, Revolutionary Guards officers and plainclothes intelligence and paramilitary volunteer members in the streets have made it impossible for protesters to congregate.

The government also began a propaganda campaign aimed at shifting responsibility for the violence meted out by the state onto foreign powers and the protesters themselves. State television aired a program in which witnesses and experts all agreed that Neda Agha-Soltan — the 27-year-old bystander whose death was captured on YouTube, sparking sympathy worldwide and turning Neda into a martyr — was shot by foreign agents in order to intensify people's rage. State television also broadcast another program mourning the purported deaths of eight Basijis killed by bullet wounds.

The Basij, or Basijis — the paramilitary volunteer force developed by the Islamic republic to protect the Islamic revolution from civil disturbances like the kind that have occurred these past weeks — have had an overwhelming presence on Tehran's streets, often setting up roadblocks to check cars and detain people they consider suspect. They have also been brought in as reinforcements for the police in dealing with demonstrators. Although they are an official subdivision of the Islamic Republic Revolutionary Guards Corps and are decked out with crowd-control gear as well as small weapons in some cases, they are barely held accountable for their deeds and are freer in meting out violence. The majority of recent deaths of protesters are thought to have been carried out by Basijis.

But now the question is being raised: What branch of state security is behind the violence against protesters?

Both the Basij and the Revolutionary Guards Corps (or Sepah) were founded in the first year of the Islamic republic in 1979, following a decree by Iran's first Supreme Leader, Ayatullah Ruhollah Khomeini. "From the start, the Sepah was about building a popular army, one that had the duty to protect the Islamic republic from within," explains Moshen Sazegara, a founder of the Revolutionary Guards who later fell out with the regime and currently resides and works as a journalist in the U.S.

Today the Sepah is estimated to have 125,000 forces, while the Basij — which by Imam Khomeini's initial intentions was to comprise "20 million" — is estimated to number up to 6 million and is active in most cities, towns and villages across Iran. The majority of Basijis are involved in volunteer services at mosques.

Over the years, however, certain units among the Basij were trained for state control purposes. In 1999 they appeared prominently as shock troops in quelling urban dissent after student demonstrations that initially sought greater freedom for the press. "Increasingly, Sepah used the Basij as a force for indoctrination and in the role of a watchdog group on campuses, factories and even tribal units," says Frederic Wehrey, adjunct senior policy analyst at the Rand Corp., who has done several joint studies on the Sepah. "The aim was to militarize civil society to prevent currents that the Islamic republic is opposed to."

"These past weeks," Sazegara estimates, "the state has used about 12,000 such plainclothes forces in addition to another 28,000 official police and Sepah forces to control the dissent."

But Sazegara sees the possibility for division. "Many of the commanders in the Sepah have children who are in their 20s and who have joined the recent protests," he told TIME. Since Ahmadinejad took office in 2005, the Supreme Leader swapped out most wartime commanders in the Sepah, replacing them, in Sazegara's words, "with a bunch of yes-men."

"There are many Basijis who were in support of Mousavi," says an Iran-based analyst who was previously an active member of the Basij and who requested anonymity. "Many Basijis are upset that the recent violence has been attributed to them."

Former Sepah founder Sazegara concurs, adding that many of the plainclothes men controlling the streets and meting out excessive violence to protesters are "intelligence personnel of the Sepah, some of them even with military degrees, but showing up in plainclothes to take on the appearance of the Basij."

In the face of such overwhelming force, opposition leader Mousavi has held back from calling for further protests and on Thursday said he would file for permits for future protests.