On the night of February 19, growing tension between Iranian security forces and members of the country's Gonabadi Sufi order came to a violent head in north Tehran.

The Gonabadi Dervishes had gathered that Monday in front of Police Station 102, Pasdaran Avenue, to protest the arrest of a member of their community, Nematollah Riahi, who had been detained a day before.

Clashes broke out after security forces arrived at the scene. The Dervishes said the violence was provoked by policemen and posted photos online, allegedly captured on the night, showing men with bandaged and bloodied faces.

Iranian authorities blamed the clashes on the protesters. The next day, Iranian media reported five security officers had died as a result of the violence: three police officers were killed when a white minibus, reportedly driven by a demonstrator, rammed into a crowd of riot police. In a separate incident, a member of the government-aligned Basij militia was run over by a car, and another was stabbed to death.

More than 300 Dervishes were arrested by Tuesday, Iranian media said.

Farhad Nouri, an editor of Dervish-run news site Majzooban Noor who lives in Australia, told Al Jazeera as many as five members of the Gonabadi Sufi community died as a result of the clashes.

The death toll was the highest for Iran's security forces in a single night since anti-government demonstrations in 2009.

For Iran's Gonabadi Dervishes, say analysts, it follows a pattern of persecution that has existed for more than a decade.

Potential to mobilise

Gonabadi Dervishes represent the largest of Iran's Sufi orders. Estimates of how many members belong to the religious group vary between two and five million. Nouri, who fled Iran in 2011, said as many as 10 million Dervishes live there.

The Gonabadi Sufis consider themselves Shia Muslims, but the mystical Sufi branches of Islam have a different interpretation of the Quran.

"With any alternative faith, whether it's Dervishes or Baha'i or others - they see it as a threat to their official religion," said Omid Memarian of the New York-based Center for Human Rights in Iran.

"Dervishes have been under a lot of pressure by the government in exercising their beliefs over the past years. The government is using these protesters to discredit them."

Sufism is very deeply rooted in the Iranian culture. They're not that different from the way that Iranians pursued Islam in its early years Tara Sepehri Far, Human Rights Watch

Tara Sepehri Far, an Iran researcher with Human Rights Watch, said the rift between Iranian authorities and the country's Gonabadi Sufi order is not just over interpretations of Islam.

"This community has a long history of being persecuted," she said. "Sufism is very deeply rooted in the Iranian culture. They're not that different from the way that Iranians pursued Islam in its early years.

"Most of their efforts have been peaceful in the past, but they have the potential to mobilise."

Relations soured

The Gonabadi order enjoyed a fair degree of tolerance in Iran even after the Islamic Revolution, which put the Shia clerical order at the top of Iran's power structure. The current "qutb", or grand master, of the Gonabadi Dervishes, Nour Ali Tabandeh, 90, was at one point a deputy culture minister and deputy justice minister.

But relations between the Gonabadi Sufis and Iranian authorities took a tumble shortly after hardline former President Mahmoud Ahmadinejad took power.

In 2006, a Sufi lodge was destroyed in Qom, and more than 1,000 dervishes were reportedly arrested after a high-ranking cleric, Ayatollah Hossein Noori-Hamedani, called the religious order a "danger to Islam".

Usually, the Dervish aren't politically involved. Their only political act is participating in elections and voting for reformists Saeid Golkar, senior fellow on Iran policy at the Chicago Council on Global Affairs

"The hardline [clerics] realised after Ahmadinejad was elected they now had a partner in the executive branch that supported their plan to expel Sufis from the city of Qom," said Saeid Golkar, a senior fellow on Iran policy at the Chicago Council on Global Affairs.

In 2009's controversial election, which was ultimately won by Ahmadinejad amid widespread allegations of fraud, Tabandeh publicly backed reformist presidential candidate Mehdi Karroubi, deepening the rift between himself and Iran's established order.

"That was another moment that the hardliners, both in the military and security apparatus and the clergy came together and said 'We have to push this group back'," said Golkar.

"Usually the Dervish aren't politically involved. Their only political act is participating in elections and voting for reformists.

"There are millions of Sufi followers in Iran, and they follow their leader. These millions of people can impact any election."

In recent years, persecution of Gonabadi Dervishes has continued. Two more places of worship in Borujerd and Isfahan were destroyed after the one in Qom.

A 2014 report by the UN's special rapporteur on the human rights situation in Iran said authorities had "targeted" Dervishes with "arrest, prosecution and judicial harassment". At least 970 Gonabadi Dervishes had been prosecuted since 2008, the report said.

Over the years, there have been reports of Gonabadi Dervishes being dismissed from their jobs and banned from universities for belonging to the religious order.

Concerns for those arrested

The violence on the night of February 19 followed a number of recent incidents that put Iranian authorities at odds with the country's Gonabadi Sufi community.

Tensions had flared up in December when five Sufi activists belonging to the Gonabadi order were reportedly arrested by Iranian authorities and transferred to Evin prison amid renewed anti-government protests during which dozens were killed and hundreds detained.

And on February 4, clashes had taken place between Dervishes and members of the Basij after intelligence and security agents reportedly surrounded Tabandeh's house, prompting fears he would be arrested.

Golkar said the timing of increased pressure by Iranian authorities on members of the religious order might have to do with upcoming parliamentary and presidential elections, to be held in 2020 and 2021, respectively.

"It's part of a tactic the hardliners started using immediately after Rouhani won the election [in 2017]. They realised they have to do something.

"Hardliners are not attractive to the middle class and educated Iranians. But they can anger and disappoint them to the point that they bypass the election," said Golkar.

Within Iran, some have said the violence was directed from outside the country. Tehran Metropolitan Police Deputy Brigadier General Hassan Rahimi reportedly claimed the "rioters" had been "puppeteered by foreign hands and foreign-based anti-establishment terrorists".

A lot is still unclear about what exactly happened on the night of February 19.

Nouri maintained there is no "conclusive evidence" that Dervish protesters were behind the wheel of the bus and car that killed the three police officers and Basij forces on the night of February 19.

"Dervishes are recognised as pacifists with no interest in violence and causing human suffering. It is highly unlikely that they have been involved in this incident," he told Al Jazeera.

President Hassan Rouhani condemned the attacks, saying "violent behavior and insults against the police force, which is in charge of maintaining public order and security, will not be tolerated under any circumstances," according to Press TV.

Interior Minister Rahmani Fazli said those "disrupting the security" would be "treated decisively", but also offered a more conciliatory tone.

"We believe the Dervish community across the country is tending toward moderation and prudence," Radio Farda quoted him as saying.

"We definitely do not attribute the incidents on Pasdaran Avenue to the Dervishes."

But some hardliners took a harsher stance.

Noori-Hamedani called the Dervishes "devious, in the wrong, and liars", Radio Farda reported.

Another senior cleric, Naser Makarem Shirazi, reportedly warned: "Iranian officials should be cautious on what they say and avoid comments against religious teachings that will backfire."

Observers have meanwhile expressed concerns about the treatment of the more than 300 Dervishes who were arrested, some of whom have now reportedly been released.

Reporters Without Borders (RSF) on February 22 said they were "extremely concerned" about two journalists who were among the arrested. Reza Entesari and Kasra Nouri, two reporters for Majzooban Noor, had reportedly been beaten before they were taken in by police, with some saying they are now in a coma.

"The lack of transparency and denial of justice surrounding their arrest and hospitalisation is unacceptable," Reza Moini, the head of RSF's Iran desk said.

HRW's Sepehri Far mirrors these concerns.

"These arrests, just the magnitude itself signals arbitrariness," she told Al Jazeera.

"We are worried about the charges these people are going to face. The record of Iran's abuse in cases like these is concerning."