The execution of Sheikh Nimr al-Nimr has brought new attention to the relatively obscure and precarious Shiites of Saudi Arabia, as I wrote Tuesday. But what about Sunnis in Iran? Just as Saudi Arabia is practically synonymous with Sunni Wahhabism, Iran—the world’s largest Shia country—is the demographic and scholarly center of the sect. Yet around 9 percent of the population is Sunni.

The already-heightened rivalry between Saudi Arabia and Iran is ratcheting up, fed by Nimr’s execution over the weekend. Despite occasional insistences that this is simply the latest flare-up in a 1,400-year-old battle between Sunnis and the Shiites, the more persuasive case—as Marc Lynch points out—is that it is a battle between two rival regional powers who are exploiting sectarian differences for political gain. It is, Lynch writes, “cynical manipulation of identity politics by regimes seeking to advance their domestic and foreign policy interests. …  Sectarianism today is intense, but that is because of politics.” Regardless of the causes, the tension puts more pressure on the minority sects in each country.

First, a brief history lesson: How did Iran become Shia? Until the 16th century, Persia was mostly Sunni. At the turn of that century, the Safavid dynasty conquered much of what is now Iran and made Shiism the official religion. The conversion was accompanied by a massive crackdown on Sunnis, so that over time much of the population became Shia. Today, most of the Sunnis who remain are mostly from minority ethnic groups—Arabs, Turkmen, Kurds, Baluch—rather than Persians. That makes some discrimination based on religion difficult to separate from ethnic discrimination, according to the U.S. State Department. Many of these Sunnis also live in remote, impoverished areas, making it difficult to tell whether poor government services are a result of sectarian discrimination or not.

The state of religious freedom in Iran is not good—Freedom House ranks it “not free,” with nearly the lowest rating, in its annual report. (That’s still enough to best Saudi Arabia, which Freedom Houses places in the “worst of the worst.”) In addition to Sunnis, there are several smaller non-Muslims groups, notably Bahais, Jews, Christians, and Zoroastrians. Compared to them, Sunnis have greater legal protections. Sunni schools of Islamic jurisprudence are officially recognized in the constitution as sources of family law and religious education. Sunnis can serve in the parliament, though they’re not afforded the few reserved seats given to other religious minorities.

In practice, however, the status of Sunnis appears more precarious. As of the end of 2015, the State Department said there were hundreds of religious minorities, including Sunnis, imprisoned. Sunnis complain that though there are an estimated 1 million of them in Tehran, there are no Sunni mosques in the capital. In addition, the State Department noted in its most recent annual religious-freedom report that religious readers had said Sunni literature and teachings were banned in public schools, and new construction of Sunni mosques and schools was banned. Also:

There were reports of arrests and harassment of Sunnis. The International Campaign for Human Rights in Iran (ICHRI) cited activist reports that authorities in Ahvaz arrested 20 Arab-Iranians February 26 for converting from Shia Islam to Sunni Islam, arresting them in a house raid without a warrant and then detaining them in an MOIS office. Mohammad Kayvan Karimi, Amjad Salehi, and Omid Payvand were sentenced to death May 4 on charges of “enmity against God through spreading propaganda against the system.” According to Human Rights Activists News Agency (HRANA), the three were active in preaching Sunni Islam.

In addition, Iranian Sunnis reported raids on worship sites, and being prevented from celebrating Eid al-Adha in 2014. Last summer, clandestine worship spaces for Sunnis in Tehran were reportedly destroyed.

One way that Sunnis—as well as disaffected non-Sunni members of Iranian society—have responded to this environment is to embrace Salafism, hardline Sunni orthodoxy, according to Mehdi Khalaji, a fellow at the Washington Institute for Near East Policy. The Internet has allowed Salafis to spread their ideas and create networks throughout the country. “This is one of the reasons why the regime does not allow Sunnis to build mosques in Tehran or other large cities—it is deeply concerned about Salafis using them to recruit young Shiites who are frustrated with the Islamic Republic’s ideology,” Khalaji wrote in 2013. They also often have ties to Iran’s regional foes, especially Saudi Arabia. “Given these factors and the increasing resentment among Iran’s Arab, Kurdish, and Baluch population, the growth of Salafism is a clear security threat to the regime.”

Nonetheless, President Hassan Rouhani promised during his 2013 campaign to improve religious freedom and tolerance, and he fared particularly well in voting in regions with heavy Sunni representation. Rouhani has since repeated his desire to improve Sunni-Shia relations, and the government has trumpeted its outreach. However, the 2015 annual report of the U.S. Commission on International Religious Freedom concluded that “President Hassan Rouhani has not delivered on his campaign promises to strengthen civil liberties for religious minorities,” citing, among other things, the growth in the number of Sunni Muslims imprisoned for their beliefs.

The growth of ISIS, which is Sunni, doesn’t make Iran’s opening up to Sunnis any more likely—especially when taken with a fear of growing Salafism within the country, and paired with widespread (but unsubstantiated) belief in parts of the Middle East that the Saudi government is funding ISIS. In November, Iranian authorities said they had smashed an ISIS-affiliated cell in Western Iran, in a Kurdish Sunni province.

Along with the new tensions with Saudi Arabia, all of this points to a more difficult life for Sunnis in Iran in the near future—perhaps pushing more of them toward Salafism. That’s the trouble for both Saudi Arabia and Iran in stoking tensions for geopolitical gain: The motives may be cynical and strategic, but the sectarian strife they foment isn’t easily put to rest.