T HE STREETS are quiet and the tear gas has dissipated, but no one knows for sure how many protesters were killed in Abuja, Nigeria’s capital, at the end of October. The army claims six people died when soldiers stopped demonstrators from overrunning a checkpoint. Human-rights groups say at least 45 were killed—and that the demonstrations were peaceful.

More mystery surrounds the group that organised the protests, the Islamic Movement in Nigeria ( IMN ). It is known to be made up mostly of Shia Muslims. Analysts count millions of members. Many gathered in Abuja to demand the release of their leader, Ibrahim Zakzaky, who was jailed three years ago. He preaches non-violence, but the army is testing the IMN ’s restraint. Some fear the government is creating a new Boko Haram, the Sunni jihadists waging a bloody insurgency in the north.

There were few Shias in Nigeria 40 years ago. Mr Zakzaky is almost single-handedly responsible for changing that. Entranced by the Iranian revolution, he converted from Sunni Islam to Shiism in 1979, then went about converting others. Today analysts think Nigeria has up to 3m Shias; nearly all are in the IMN . They form a small minority of Nigeria’s roughly 180m population, split between Muslims (mostly Sunnis), who dominate the north, and Christians, who dominate in the south.

Mr Zakzaky has amassed followers in the impoverished north by railing against the government’s ineffectiveness and corruption (while extolling the virtues of Iran). Many are drawn to the IMN ’s schools and welfare schemes. But it has evolved into something of a messianic cult, centred around Mr Zakzaky. Similar groups have a long history of stirring up trouble in the north. The IMN ’s rise coincided with that of the Yan Tatsine cult, which followed a preacher called Maitatsine and clashed with the government in the 1970s and 80s. Now Boko Haram, which is much smaller than the IMN , torments the state.

For most of its existence, the IMN was largely ignored by the government. That changed when members blocked the Nigerian army chief’s convoy in the state of Kaduna in 2015. At least 300 of them were killed when soldiers cleared the road, say human-rights groups. (It is not clear if the soldiers were attacked.) Mr Zakzaky and his wife were injured, then arrested. For two years they were held without charge, despite a court order in 2016 to release them. In April they were charged, implausibly, with conspiracy to kill the army chief. The IMN , now banned in Kaduna, has vowed to keep protesting until Mr Zakzaky and his wife are released. On November 7th they were denied bail by Kaduna’s high court.

The government’s response is starting to resemble its tactics against the Yan Tatsine and the forerunner to Boko Haram, which caused both groups to become more violent. “The state is going about this in the wrong way,” says John Campbell, a former American ambassador to Nigeria. He fears the IMN will abandon non-violence.

Others worry that the stand-off could descend into a proxy war. The IMN reportedly receives cash from Iran. The group denies this—and accuses the government of being in thrall to Saudi Arabia.