As Saudi Arabia's war against Yemen's Houthi militia enters its third week, a surge of nationalist fervour is sweeping the conservative Sunni Muslim kingdom, bringing with it a sharp sectarian edge.
The Saudi authorities have avoided using overtly sectarian language to describe the Houthis, who adhere to a Yemeni Shi'ite sect, but many clerics, journalists and social media users have shown no such restraint.
A Tweet from hardline Sunni cleric Sheikh Nasser al-Omar to his 1.64 million Twitter followers the day after air strikes were announced described Shi'ites using the derogatory term "rejectionists".
The use of such language, even by private individuals, carries risks for the kingdom in a conflict where the Houthis present themselves as defenders of a local religious tradition against Sunni extremism that they say is propagated by Riyadh.
While Yemen's complex internal conflict is not yet dominated by friction between Sunnis and Shi'ites, Yemeni analysts have repeatedly warned that sectarianism is a growing danger and could lead to a dangerous escalation in fighting.
Many Saudis have characterised the strikes against the Houthis as Riyadh assuming the mantle of Sunni leadership in what they see as a long-overdue response to a perceived decade of Iranian aggression in Arab countries using Shi'ite proxies.
Local press reporting on the military campaign, officially known as "Operation Decisive Storm" has overwhelmingly portrayed it as successful, largely ignoring reports of civilian casualties while lavishing praise on the kingdom's rulers.
National identity in Saudi Arabia is closely bound up with the strict Wahhabi Sunni school, which views Shi'ism as heretical, and whose leading clerics sometimes publicly cast doubt on whether Shi'ites are truly Muslim.
The government has in recent years striven to avoid openly sectarian language itself, and sent princes and senior officials to attend the funeral of Shi'ites killed by Sunni militants in an attack in November.
Last year it detained a cleric who had posted Tweets celebrating the killing of Houthis by al Qaeda members in Yemen using explicitly sectarian language.
'LIKE THE LION ATTACKS HIS PREY'
However, members of the Shi'ite minority complain of systematic discrimination. Riyadh denies this but Saudi Arabia's state-appointed religious establishment makes frequent attacks on the sect's doctrines and history.
"If they (Shi'ites) manage to win and control the state, they ravage Sunnis: clerics, women, children, the rulers and the ruled. They attack just like the lion attacks his prey," said Farid al-Ghamdi, a cleric at Mecca's Umm al-Qura seminary in a sermon visible on YouTube.
That kind of scare-mongering has been evident in the Saudi press as well.
A report in the daily al-Medina newspaper last week cited "military experts" as saying the Houthis wanted to turn Yemen's capital Sanaa into "an entirely Shi'ite city by 2017" and that the air strikes would thwart "this Iranian plan".
Sunni social media users and clerics often align Shi'ites with Tehran by using the term Safavid, the 16th century Persian dynasty that popularised Shi'ism in Iran, which plays on both sectarian and Arab nationalist sentiment.
Yemen's Zaydi Shi'ite sect is very different to the Shi'ite school followed in Iran, and while the Houthis have clear links to Tehran, they appear to be more independent of Tehran than its proxies elsewhere in the region.
But in the fevered atmosphere of a military campaign, such distinctions have a habit of disappearing.
"Decisive Storm came to sever any ambition of the Safavids to besiege Muslims in their own homes," wrote cleric Saad al-Breik to his 1.15 million Twitter followers after the air strikes began last month.