How IS seeks sectarian war in Saudi Arabia
Saudi Arabia has now suffered three deliberate attacks by supporters of Islamic State (IS) on the restive Shia Muslim minority living in the country's oil-rich Eastern Province.
The first, in November 2014, was a gun attack. And, in May 2015, there have been two devastating suicide bomb blasts targeting worshippers at Friday prayers.
The last two attacks used RDX, a powerful military explosive, and have been claimed by IS's self-styled Najd Province, named after Saudi Arabia's staunchly conservative Sunni heartland, the desert plateau in the middle of the country.
So what is IS trying to achieve and will it succeed?
These attacks are a watershed for Saudi Arabia.
How it reacts now and in the coming months will determine whether the largest and most important Arab state can stave off a wider sectarian conflict between the country's majority Sunni and minority Shia Muslim populations, something that would be disastrous for both communities.
The attacks follow decades of state and religious discrimination against the Shia minority, who constitute about 10% of the population.
Even a senior royal, Prince Abdelaziz Bin Salman Al-Saud, whose father is now king, admitted to me in an interview in 2013 that the Shia of Saudi Arabia had a legitimate grievance and that their situation needed addressing.
Since then, there have been deadly clashes between police and protesters in Eastern Province, and tensions there had only just started to subside.
The Shia are considered by many ultra-religious Saudi Arabian Sunnis to be heretics, outsiders suspected of being more loyal to Iran than to Saudi Arabia, and recently there have been a number of vitriolic speeches and sermons demonising them as apostates.
This narrow, discriminatory view is shared by IS, which despises the Shia even more than it does Christians, and it has frequently targeted Shias in both Iraq and Syria.
"[IS] is trying to weaken the Saudi state by claiming the conservative Salafi Sunni mantle," says Nawaf Obaid, a Harvard senior fellow.
"They will fail, as al-Qaeda did 10 years ago."
So far, the new Saudi Arabian leadership has reacted with surprising speed and sensitivity.
He allowed Saudi Arabian television to broadcast the massively attended Shia funerals in full.
On 3 June, he referred to the Shia volunteers who had died preventing the second bomber from entering the mosque in Dammam as "martyrs" and "heroes" - a significant step for the absolute monarch in a country that has never had a senior Shia minister and where the authority of the ruling family rests on the support of the arch-Sunni clergy.
"[The Saudi leadership] may be saying the right things to calm the situation," says a Saudi Arabian Shia, who asked not to be named for his own protection.
"But all the calls by the Shia leadership for the government to crack down on anti-Shia rhetoric have been ignored.
"These are a precursor to attacks like the ones we have just seen."
IS has come into this delicate diplomatic minefield, with guns blazing and bombs blasting.
It would like nothing better than to trigger a fully blown sectarian war between Sunni and Shia in Saudi Arabia, which is home to the two holiest sites in Islam, in Mecca and Medina.
IS likes to present itself to Sunnis as being the sole force in the region capable enough and willing to push back against the creeping advance of Iran's Shia allies.
As part of that narrative it would like to pull in more of the mainstream Sunni population behind its banners to resist what it sees as a heretical Persian-inspired apostate creed.
Saudi Arabia demographics:
The population is estimated at 29.8 million, of which about nine million are foreigners
Sunni Muslims make up the majority of the indigenous population, 75-90%
Shia Muslims make up the remaining 10-25%
"Shia-Sunni relations in Saudi Arabia are already under severe strains due to events in Iraq and Syria, as well as Saudi Arabia's campaign in Yemen against the [Shia] al‐Houthi [rebels]" says Aimen Deen, an expert on jihadist movements.
"Therefore IS will seek to provoke the Shia minority to retaliate or at least take to the streets in violent protests."
More attacks likely
Mr Deen predicts more attacks by IS inside Saudi Arabia to further provoke a reaction from elements of the Shia protest movement.
He does, though, point out that the Saudi-led air campaign in Yemen against Shia rebels seen by many Saudis as Iran's proxy militia is so popular with much of the Saudi population that recruitment of Saudis to IS has fallen off dramatically.
And what if IS persists in its attacks anyway?
Nawaf Obaid believes the government is capable of dealing with it, bearing in mind that the current crown prince is the man who led the successful anti-al-Qaeda campaign for many years.
"The remarkable Saudi counter-terrorism programme will defeat [IS] and the legitimacy of the Saudi state will only be reinforced," he says.
That prediction is likely to be tested in the coming months.