By William Maclean, Security Correspondent
LONDON, Dec 12 (Reuters) - Swedish police investigating two blasts that rocked central Stockholm, killing the suspected bomber and wounding two people, said on Sunday they had good leads into what they said were "terror crimes". [nLDE6BB04J]
Here are questions and answers about possible perpetrators and tactics favoured by militant groups.
WHAT ARE THE THEORIES ABOUT THE PERPETRATOR?
He has not yet been identified by authorities. The main publicly available clue is a message sent to authorities before the attack that linked it to Sweden's military presence in Afghanistan and a cartoons controversy.
That suggests the perpetrator is involved in violent Islamism of the type promoted by al Qaeda.
A Swedish broadcaster, citing unidentified sources, said the dead man was thought to be a 29-year-old from a small town in southern Sweden, but it gave no other details.
IS HE FROM SWEDEN'S IMMIGRANT MINORITY?
Not necessarily. Attacks of this type in the West have sometimes been carried out by Western converts to Islam radicalised by reading extremist websites and associating with militant Islamists in their social life.
IS HE LIKELY TO HAVE ACTED ALONE OR IN A GROUP?
True "lone wolves" are rare. Experience from other attacks shows assailants usually have some support, even if it is only encouragement from like-minded associates. But attacks have happened without the perpetrators taking formal instruction from militant groups in a hierarchical chain of authority.
"These things rarely happen in isolation so I suspect the authorities in Sweden will be looking at who else was involved with this particular person," said Henry Wilkinson, terrorism specialist at Janusian security consultancy in London.
DO FORMAL LINKS TO MILITANT GROUPS MATTER?
Less than they did. Al Qaeda uses various attack models.
- Plots coordinated from the central leadership. Examples, investigators say, are suspected conspiracies uncovered in the past 18 months in the United States, Norway and Britain, which law enforcement officials say were directed by a group of operatives in the core leadership's bases in Pakistan.
- Conspiracies hatched by affiliate group. Examples are a plan by the Yemen-based al Qaeda in the Arabian Peninsula (AQAP) to conceal bombs inside office equipment and mail the packaged items air freight to America. The plot was uncovered and foiled.
- The "home-grown" attacker who, fired up by ideological fervour, strikes out using whatever weapon is to hand. Examples include U.S. Army psychiatrist Major Nidal Malik Hassan who killed 13 people in a shooting spree in 2009.
WHO ARE THE MAIN ISLAMIST MILITANT GROUPS TARGETING EUROPE?
For militant groups suspected of involvement in attack plots in Europe, click on [ID:nLDE69B1NS]
For recent major militant attacks in Europe, click on [ID:nLDE6920CK]
Al-Qaeda aligned groups, many based in Pakistan, Yemen and Somalia, can provide training and money, although their capacity to do so in formal training camps is constrained by attacks from the U.S. military and by U.S.-backed government forces.
Al Qaeda's leadership, increasingly restrained by missile strikes from U.S. drones in northwest Pakistan, prizes "home-grown" recruits as they have Western passports and can travel overseas easily, experts say.
ARE THE CARTOONS STILL AN ISSUE?
Very much so. The message cited Afghanistan, where Sweden still has troops, but also mentioned Western media cartoons of Prophet Mohammad published several years ago. Muslim anger at them is kept alive by al Qaeda propaganda to help radicalise and recruit, says Lorenzo Vidino, a specialist in Islamism and political violence in Europe at the RAND Corporation think tank.
HOW WILL THE ATTACK BE SEEN ELSEWHERE IN EUROPE?
This will heighten vigilance among security officials.
The incident follows several testing months for European governments after a U.S. travel alert about possible attacks by militants and the failed AQAP plot involving air cargo.
German authorities last month said they were on guard against threats of armed attack on civilians of the kind that killed 166 in the Indian city of Mumbai in 2008.
"Other European capitals must be worried about the fact that this happened in a capital city in the run-up to Christmas," said Claude Moniquet, head of the European Strategic Intelligence and Security Center think tank in Brussels.
"It could be a signal to other potential attackers to prompt them to attack at this time."
IS TERRORISM RISK HEIGHTENED AT CHRISTMAS?
Moniquet says there is heightened sensitivity in the West to the possibility of an attack around Christmas because of a failed attempt by a Nigerian Islamist to destroy an airliner over Detroit on Dec. 25, 2009 on a flight from Amsterdam.
The attack was praised by al Qaeda which argued that the apprehension, disruption and security costs it had generated had helped publicise the group's anti-Western message. (Additional reporting by Niklas Pollard; Editing by Janet Lawrence)
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