(CNN) -- The deadly bombings in Uganda's capital may have heralded a chilling new chapter in the history of a Somali Islamist group with links to al Qaeda.
For almost four years the radical al Shabaab movement has been engaged in a violent struggle with the U.N.-backed transitional government for control of Somalia, which has had no effective administration since Mohamed Siad Barre's regime collapsed in 1991.
But the weekend bomb attacks in Kampala that killed 74 people would mark the first time the group has claimed responsibility for an operation beyond the Somali border, apart from sporadic attacks across the border into northern Kenya.
Al Shabaab, meaning "the youth" in Arabic, advocates the strict, often brutal, Saudi Arabian-inspired Wahhabi interpretation of Islam. It emerged in 2005 as the militant youth wing of the Islamic Courts Union (ICU), which briefly controlled much of the Horn of Africa nation before being ousted in 2006 by troops from neighboring Ethiopia.
While most of the ICU's leaders fled, al Shabaab fighters under leader Ahmed Abdi Godane remained behind to wage a guerilla-style war against the invading force.
The U.S.-backed Ethiopians remained until early 2009 when the Transitional Federal Government (TFG) took tentative control, clinging to a small part of the capital, Mogadishu. They were supported by African Union (AU) peacekeepers mainly from Uganda and Burundi.
By contrast al Shabaab won control of much of central and southern Somalia, while their growing ties with Osama bin Laden's al Qaeda terror network gave them valuable manpower and resources. In March last year bin Laden issued a statement calling for Muslims everywhere to "help the Somali mujahedeen fight until Somalia is an Islamic state."
According to the transitional administration in Mogadishu the burgeoning relationship with al Qaeda led to an influx of militant fighters from abroad.
"With regard to the fighting that's going on in Afghanistan, in Pakistan and in Yemen, some people are looking for a place to hide and Somalia is a good candidate for that," Somali President Sheikh Sharif Sheikh Ahmed told CNN in April.
Ahmed, once a senior, moderate figure in the ICU, said al Shabaab has also reached out to the Somali diaspora living in the West, radicalizing young Muslims via the Internet and encouraging them to move back to the country to join the "Jihad." The group have become particularly adept at using the media in this way to announce details of attacks that it has carried out.
Senior African Union military figures say the signs of al Qaeda's hand in the fighting are visible through the use of Improvised Explosive Devices, or IEDs, and suicide bombings.
But it is al Shabaab's mutation from nationalist insurgents to fully-fledged terrorist organization that has been most significant, according to Rashid Abdi of the International Crisis Group.
"If you look at the rhetoric and language and if you look at the Web sites, if you hear their preachers or their scholars speak, it is completely indistinguishable from al Qaeda leaders," Abdi said.
Uganda's recent involvement in Somalia makes it unsurprising that a newly "internationalized" al Shabaab would eventually target them, according to analyst Alex Vines, from London-based think tank Chatham House.
"Al Shabaab are the leading point of inquiry because of its previous threats against Uganda and because of its contributions to the African Union Mission in Somalia (AMISOM) and the presence of the EU training mission in Mogadishu," he told CNN.
In March, the New York Times reported that the U.S. had become so concerned with the group's activities across Somalia and in Yemen, across the Gulf of Aden, that they were giving direct military support to the TFG. This was strongly denied in Washington.
But al Shabaab's growing reach also indicates that they have a consistent income stream. In addition to money being sent from sympathetic Somalis and Muslims in the West, there's growing evidence the group are benefiting from the explosion in piracy off Somalia. Piracy expert Andrew Mwangura believes many pirates may be "fronting" crime syndicates based around the Mideast, with ransom cash eventually filtering through to Islamist fighters who control much of Somalia's coastline.
Al Shabaab is believed to number up to 7,000 armed men, with a main force of around 3,000 fighters with well-honed guerrilla skills, according to Agence France-Presse. It comprises an armed wing, known as the Jeish al-Usrah (Army of Suffering), as well as a religious police or propaganda arm known as Jaysh al-Hisbah (Army of Morality).
Jane Ferguson contributed to this report.