Mogadishu, Somalia (CNN) -- In Somalia's enduring chaos, militant groups have for years come and gone. Today's most powerful -- Al Shabaab -- are much more menacing, say those in Mogadishu.
In Arabic, Al Shabaab means "the youth," but it is too far-reaching to be just a rabble of youngsters. It controls much of central and southern Somalia and large parts of the capital Mogadishu.
And after years of pledging allegiance to al Qaeda, Al Shabaab formalized the relationship in February. Since then, the Somali government says there's been an influx of foreign fighters.
"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," said Somali President Sheikh Sharif Sheikh Ahmed, who leads the weak, U.N.-backed Transitional Federal Government (TFG).
Ahmed was once a senior, moderate figure in the Union of Islamic Courts -- an alliance that included Al Shabaab and which held power in Somalia for six months in 2006 before being overthrown by Ethiopian forces.
The Ethiopians remained until early 2009 when the TFG took tentative control, clinging to a small part of Mogadishu, and protected by African Union (AU) peacekeepers mainly from Uganda and Burundi.
A quiet figure, President Ahmed sits in his office at the palace grounds while government troops outside fire warning shots to prevent people from venturing too close.
"We used to estimate the number of foreign fighters to be between 800 and 1,200 but that number seems to have been growing," he said.
Al Shabaab has reached out to Somalis living in the West, radicalizing young Muslims via the Internet and encouraging them to move back to the country to join the Jihad.
In November 2009, eight Somali-American men from the U.S. state of Minnesota were charged with offenses including attending Al Shabaab terrorist training camps and fighting for the group. In August 2009 two Somalis were arrested in Melbourne, Australia, for allegedly planning a suicide attack on a military facility.
And a naturalized-American suicide bomber, who blew himself up killing 29 people in October 2008, was born in Somalia.
Although the suicide attack took place in Northern Somalia, there is a growing debate as to whether those Somalis living in the West who are recruited by Al Shabaab may return to the U.S., Canada or Europe to stage attacks.
"[Somalia is] a place to hide and a place to fight, not only with the West but with anybody who disagrees with them," said the president. "They go from place to place but their objectives don't change, they fight people of all persuasions."
This is commonly noted by Somalis who talk about Al Shabaab -- they not only violently oppose the West, but also other Somalis who don't support their war.
"If you are not with them, you are against them," said one official at Mogadishu Airport when asked to describe the group's outlook.
Many Somalis live in fear of even appearing to dissent from the group's orders.
At the African Union base they opened the military hospital to the public in response to the lack of medical facilities in the city. When they run out of drugs and instead issue prescriptions, even the desperately ill throw them away, knowing the risks of being caught with such evidence of "collusion."
In February, the group banned the U.N. World Food Program, even though millions rely on food aid for survival.
Music and radio stations have been banned as well as school bells, which were recently declared too Christian by Al Shabaab and their allies.
Stories of the brutal nature of their control over the city's streets make their way through the hospital staff and into the A.U. camp.
Tales of dismemberment, bodies being chopped up and sent back to families, routine executions, even people being skinned alive emanate from neighborhoods closed off to the international community or any form of governance.
Leaning over the wall of a lookout post at the notorious Kilometer Four junction, one soldier points to a minaret. "That's the Red Mosque," he says. "That's where they chop people up."
Such a fate is often promised to Major Ba-Ho Ku, the Ugandan spokesman for the peacekeepers.
Callers to his cell phone promise death and dismemberment. He dismisses the group as misguided and accuses them of making the lives of ordinary Somalis horrific.
"It's so sad," he says, hanging up on another sinister voice. "They don't know what they are doing. They are just killing their own people."
It is estimated that around half the population of Mogadishu have fled to refugee camps.
Those left behind are caught in an increasingly deadly form of urban warfare. Senior A.U. 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.
Most of the fighting goes on between the local TFG forces, weak and underfunded, and Al Shabaab.
At the A.U.'s hospital the morning after a skirmish in town, TFG soldiers lie of stretchers, thin and bleeding. Colonel Dr James Kiyengo, a surgeon, leans over one soldier injured by an IED.
"This kind of injury has increased," he says. "Earlier on the soldiers could move out of the camp and come back, and when the Ethiopians withdrew there was a vacuum that was filled.
"I think the insurgents came closer, and into the city, such that we found that these injuries increased. Earlier on there were no IEDs, not as common as it is now."
A major offensive against Al Shabaab to retake large areas of the city has been rumored for months. Military leaders in Mogadishu play down the reports, saying the move against Al Shabaab will happen gradually.
Last month 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.
"The United States does not plan, does not direct, and does not coordinate the military operations of the TFG, and we have not and will not be providing direct support for any potential military offensives," Johnnie Carson, Assistant Secretary of State for Africa, told reporters. "Further, we are not providing nor paying for military advisors for the TFG. There is no desire to Americanize the conflict in Somalia."
The U.S. has admitted sending indirect military support to both Somalia and Yemen to fight al Qaeda-linked Islamic militants in the region.
That includes sending weapons and ammunition to Somalia's transitional government which the United States says is in accordance with U.N. Security Council resolutions that ban some arms shipments to Somalia
The dull whir of a nightly drone circling Mogadishu's skies however only adds to speculation amongst locals.
"The American's gather intelligence," one official whispered. "But they don't share it with the Somali government."