AT A time when Saudi Arabia’s aged rulers worry about their Sunni-majority population being inspired by the jihadists of Islamic State (IS), it would hardly seem wise to antagonise the Shia who make up the remaining 10-15% of their people. Yet that is exactly what a Saudi court did on October 15th, when it sentenced to death Nimr Baqir al-Nimr, a prominent Shia cleric. The shock ruling instantly prompted street protests in the largely Shia populated Eastern Province, where most of the kingdom’s oil is produced. The move threatens to reignite sectarian violence that has erupted periodically over recent decades, as well as to sour efforts to sooth Sunni-Shia tensions across the wider region. The head of Iran’s armed forces warned Saudi Arabia that it would “pay dearly” if the execution were carried out.

A powerful orator, 54-year-old Sheikh Nimr emerged as a leader of protests that broke out in 2011 in response to the violent suppression of the pro-democracy movement in neighbouring Bahrain. The island kingdom, whose predominantly Shia population is ruled by a Sunni dynasty, is linked to the Eastern Province by a causeway. In sermons Mr Nimr did not only denounce the Bahraini clampdown, which was bolstered by troops from Saudi Arabia and other Sunni Gulf allies. He also demanded greater rights for Saudi Arabia’s own disenfranchised Shias, who have long complained of discrimination in government jobs and education, as well as of being demonised by official media. The first Shia minister in Saudi history was only appointed in June this year.

Mr Nimr was careful not to incite violence, telling protesters to use peaceful means only. He also insisted that Sunnis as well as Shias were victims of similar repression, condemning the Iranian-backed regime of Bashar Assad in Syria in the same breath as the ruling Al Khalifa family of Bahrain. But such blanket denunciations of tyranny may be exactly what angered the Saudi authorities. When police arrested Mr Nimr in July, 2012, they claimed, unconvincingly, that the four bullet wounds he received in his leg had been the result of an exchange of gunfire.

The Saudis may wager that the harsh sentence is more likely to act as a deterrent than become a cause for continued protest. Much has changed in the two years since Sheikh Nimr’s arrest, which had sparked riots leading to the deaths of three protesters. Such is the fear of instability among Saudis that Shia rage has largely fizzled out over the past few months.

People point to Bahrain, whose Shias have largely, albeit sullenly, submitted to a heavily policed calm, warily contrasting this with the chaos across the border in Iraq and Syria, where sectarian hatred has added fuel to bloody civil wars. With the Saudi air force engaged in war, alongside the American-led coalition, against the Sunni fanatics of IS, Saudi Shia may confine their unhappiness for the time being to comments on Facebook.

Another calming factor, says Ibrahim al-Mugaiteeb, a human-rights activist in the eastern city of Dammam, is that the death sentence is unlikely to be carried out. Saudi Arabia tends to reserve actual executions for criminals or the likes of al-Qaeda militants who staged a bombing campaign in 2003-06. Sheikh Nimr will appeal against his sentence; and King Abdullah, who likes to be seen as the benevolent patriarch, could yet pardon him. That said, the Saudis are hardly shy of the death penalty. Last year the kingdom executed (usually by beheading) more people than any other country bar China, Iran and Iraq.