By Myra MacDonald
LONDON (Reuters) - You would probably have to go back a decade to find a cause with such potential to mobilize jihadis worldwide in a short space of time.
With images of dying Islamist protesters in media across the globe, the unrest in Egypt plays into al Qaeda's narrative of victimization, giving it an ideal opportunity to expand a strategy of exploiting instability it has already used in Libya, Syria and Iraq.
Egypt may not become an open front for jihad - the situation there is too unpredictable to say - but the violence has made it more vulnerable to bomb attacks and a rallying cry for those advocating violence to bring Muslims under sharia, Islamic law.
"If ever there's a ripe moment 2 support Al-Qaeda, it's surely now. Raising the flag in Egypt in now a priority, Insha'Allah!" the Kenyan offshoot of Somalia's al-Qaeda affiliate al Shabaab, said on its Twitter feed.
It is one of numerous posts by al Qaeda-linked jihadi groups calling on Egyptians to abandon democracy as a Western import and fight for the implementation of sharia-based government since an upsurge of violence on Wednesday.
At least 850 people have died since then in the crackdown on Muslim Brotherhood protests against the Egyptian army's intervention to oust Islamist President Mohamed Mursi on July 3.
"The mobilization of a jihadi front in Egypt serves al Qaeda's recent agenda of exploiting local conflicts to further their intent for a jihadi-led revolution throughout the region," the SITE monitoring service said.
Mursi's overthrow was a propaganda boost for jihadis like al Qaeda leader Ayman al-Zawahri, an Egyptian who had accused the Brotherhood of treachery by seeking to introduce political Islam through peaceful means rather resorting to violence.
In early August, he called for "the soldiers of the Qur'an to wage the battle of the Qur'an" in Egypt.
The worry is that some members of the Brotherhood, whose influence was demonstrated in election victories after Hosni Mubarak fell in 2011, will now be won over to the thinking of Zawahri, who intelligence sources believe is based in Pakistan.
The military, under fire from its ally and main sponsor the United States over the crackdown, says al Qaeda already has a role and firm action is the only way to stop it.
The Foreign Ministry distributed photos on Sunday showing what it said were Muslim Brotherhood members carrying clubs and firearms - and in one picture a black al Qaeda flag. A day earlier, security sources said Zawahri's brother Mohamed had been detained.
The Brotherhood denies links to the global militant network and analysts doubt hundreds of jihadis will pile into Egypt from outside, although more locals may be driven to violence.
For outsiders looking to fight, Syria is still a more attractive destination with its well-organized operations by al Qaeda affiliates Jabhat al-Nusra and the Islamic State in Iraq and the Levant.
Syria also dovetails easily with al Qaeda's anti-Shi'ite world view, projected as a battle between Sunnis and Alawite President Bashar al-Assad and his backers in Shi'ite Iran.
"It is more complicated in Egypt, though Egypt has long been important for many jihadis, and the unrest and repression will almost certainly attract jihadist attacks or drive some Egyptians toward more organized violence", said Andrew Lebovich, an academic focusing on Al Qaeda in the Islamic Maghreb (AQIM).
Apart from the lure of Syria, al Qaeda is no longer the kind of organization in which Zawahri, despite his Egyptian roots, could give top-down orders to go to fight in Egypt.
Since it was founded in the late 1980s by Osama bin Laden, al Qaeda has made itself into the most powerful of the Salafi jihadi groups, bringing in other groups as affiliates.
But it acts more as an essential link in a chain rather than a hierarchy, with different jihadi groups focusing on local and regional issues. They cooperate when it suits, are united by a common ideology and some of their leaders have shared experiences of war zones including Afghanistan.
They also have competing demands on their resources, whether it be building a presence in North and West Africa or providing expertise and an ideological core to the Pakistani Taliban waging war against the Pakistani state.
Since becoming leader of al Qaeda in 2011, Zawahri has had to balance his own interest in Egypt with the need to show he is capable of uniting all the different parts of the organization, including its powerful branch in Yemen, al Qaeda in the Arabian Peninsula (AQAP).
Inside Egypt, some fear the jailing of Brotherhood leaders will make it all the easier for younger members to gravitate towards Salafi jihadis, just as happened in earlier crackdowns in the late 20th century - among the recruits then was Zawahri.
Egypt has a history of Islamist violence: President Anwar Sadat was assassinated by Islamists in 1981, and militants killed 58 tourists at Luxor in 1997.
Suspected Islamist militants killed at least 24 Egyptian policemen on Monday in the Sinai peninsula, where such attacks have multiplied since the army takeover, while Egypt's border to the west with Libya is a convenient crossing point for weapons or foreign fighters with expertise in explosives.
Brian Fishman, a counter-terrorism specialist at the New America Foundation, said on Twitter: "Only a matter of time before a major strike, and it will be Cairo, not Sinai."
Since the overthrow of Libyan leader Muammar Gaddafi in 2011, Islamist militants, including those from AQIM, have used Libya either as a base or a source of arms supplies.
Over the past two years, an unknown number of arms have made it into Egypt from Gaddafi's stockpiles, adding to fears of instability created by the escape of hundreds of prisoners from Egyptian jails during the 2011 revolution which ousted Mubarak.
How quickly any serious jihadi violence might surface is open to debate given the speed of the Egyptian crackdown.
In Syria, the first major bombing in the capital Damascus took place in late December 2011, nine months after the uprising against President Bashar al-Assad had erupted. The Damascus blast and other attacks were later claimed by Jabhat al-Nusra.
Beyond Egypt, a shared narrative of Muslims besieged by the West - which has grown during the wars which followed the Sept 11, 2001 attacks on New York and Washington - is being fuelled by the perception, right or wrong, that the United States was complicit in the Egyptian army's crackdown by virtue of its $1.3 billion a year military aid.
Arguably, not since the 2003 U.S.-led invasion of Iraq has a development had such capacity to energize the Muslim world outside Egypt against U.S. policies, in turn helping to provide a more permissive environment for al Qaeda.
The Afghan Taliban has been one of many groups to condemn Mursi's overthrow; while far to the west, AQIM accused foreign agents of colluding with the Egyptian military and portrayed the crisis as part of a worldwide attack against Muslims.
In Pakistan, the Egyptian crackdown played into the hands of those who blame the United States and its war in Afghanistan for militant attacks in the country, hampering efforts to muster a consensus to fight the al Qaeda-linked Pakistani Taliban.
"Now we have to support Mursi," said one Pakistani diplomat, arguing that Pakistan's own painful experience of U.S.-backed military rule meant it had to speak out for a democratically elected president regardless of its views on the Brotherhood.
The crackdown in Egypt coincided with evidence that jihadi groups continued to have the power to instill fear in the West, despite a claim by President Barack Obama in a presidential campaign rally in 2012 that al Qaeda had been "decimated".
Earlier this month, the United States closed embassies across the Middle East and North Africa in response to an unspecified security threat.
(This story is refiled with Libya border to Egypt's west, paragraph 24)
(Additional reporting by Lamine Chikhi in Algiers, Jack Watling in London, Dominic Evans in Beirut, Mark Hosenball in Washington and Reuters Cairo bureau; editing by Philippa Fletcher)