But Al Shabaab is not just a small-scale rebel group with limited support. Western intelligence officials warn that the group is not just a local problem. Al Shabaab has attracted a few hundred foreigners, jihadists from countries that include Pakistan and Chechnya. Al Shabaab has also enrolled fighters from the United States and Britain.
And it is drawing funding from around the world, including from supporters in the United States.
In two separate indictments this week, five men in the United States were charged with aiding Al Shabaab, revealing an international network of support for the extremists, who are allied with Al Qaeda. The charges are the latest against a string of individuals arrested in the United States for their suspected connections to Al Shabaab.
On Wednesday, Basaaly Saeed Moalin, Mohamed Mohamed Mohamud and Issa Doreh, all from San Diego, were charged with conspiracy to provide material support to terrorists and conspiracy to kill in a foreign country.
On Thursday, Mohamud Abdi Yusuf from St. Louis and Abdi Mahdi Hussein from Minneapolis were charged with conspiracy to fund terrorists.
The United States is a big supporter of the transitional government, a U.N.-backed administration that faces daily battles against Al Shabaab in the capital Mogadishu. In February 2008 the United States designated Al Shabaab an international terrorist organization.
Three months later a U.S. missile strike in Somalia killed Al Shabaab's leader, Aden Hashi Ayro.
The charges against the men from San Diego — whose nationalities have not been revealed — allege that in late 2007 and early 2008 Moalin was “in direct telephone contact with Aden Hashi Ayro … [and] coordinated the fundraising and money transfers with Mohamud and Doreh,” according the FBI.
The indictments against Yusuf and Hussein say that the men sent funds to Al Shabaab supporters in Somalia.
On Aug. 14, others were charged with similar offenses and in June still two other men were arrested in New Jersey as they prepared to leave for Somalia. In recent years perhaps two dozen young Somali-Americans from Minneapolis have disappeared from their homes and are thought to be fighting, or have died, alongside Al Shabaab in Somalia.
Increasingly, Al Shabaab is recruiting young men of Somali descent who live in other parts of the world. Recruitment videos posted on the internet have featured an American-born commander called Omar Hammami, aka Abu Mansoor Al-Amriki, who raps over footage of Al Shabaab attacks.
Other nationalities are also involved with Al Shabaab. The recent video ‘The Crusaders’ Graveyard" shows Al Shabaab's street fighting in Mogadishu and is narrated by a masked man with a British accent.
In her first major speech on counterterrorism in London this week Britain’s new Home Secretary Theresa May said, “We know that people from this country have already gone to Somalia to fight.
“It seems highly likely, given experience elsewhere, that if left to their own devices we would eventually see British extremists, trained and hardened on the streets of Mogadishu returning to the U.K. and seeking to commit mass murder on the streets of London,” she said.
This warning echoed an earlier one given by Jonathan Evans, head of Britain’s domestic intelligence agency, in September.
He said there were a "significant number of U.K. residents” training with Al Shabaab. “Somalia shows many of the characteristics that made Afghanistan so dangerous as a seedbed for terrorism in the period before the fall of the Taliban."
"There is no effective government, there is a strong extremist presence and there are training camps attracting would be jihadists from across the world,” he added.
FBI Director Robert Mueller issued a similar warning in a speech last year.
A report published this month by London’s Royal Institute for International Affairs points to the links between Somalia and Yemen, widely regarded as the latest frontline in the war on terror and a focus of Western counterterrorism efforts.
In some ways Somalia is a vision of where Yemen might be headed: from failing to failed state.
“Yemen and Somalia face parallel challenges: insurgencies, terrorism, economic hardship and ineffective governments that are perceived to lack legitimacy,” wrote the authors of the report.
There are cultural, religious and clan similarities and while Al Qaeda in the Arabian Peninsula (AQAP) has grabbed headlines lately with the Fort Hood shootings, the failed Detroit bomber and the recent foiled attempt to bring down airplanes, Al Shabaab is the more battle-hardened fighting group.
The authors warn that existing migration routes could be used by extremists seeking to forge closer ties between AQAP and Al Shabaab. At its narrowest point only 20 miles of sea separate the Horn of Africa and the Arabian Peninsula.
Already a series of U.N. reports by investigators monitoring the arms embargo in Somalia since 2003 have detailed weapons and ammunition shipments from Yemen to Somalia.
In an interview with GlobalPost in Mogadishu, the commander of Somalia's armed forces warned of an escalation of the fighting and a staking-out of ideological grounds.
"The problem here is no longer between Somalis but between Al Qaeda and the Somali people," said Brig. Gen. Ahmed Jumale.