NAIROBI, Kenya — An unknown number of people are still being held hostage inside an upmarket shopping mall in Nairobi, more than 48 hours after Islamist militants armed with guns and grenades launched an assault on the complex Saturday.

The terror attack, which has so far killed 62 people, is the worst to hit Kenya in 15 years.

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Somalia’s Al Qaeda-linked organization Al Shabaab claimed responsibility, amid fears that radicalization is on the rise in Kenya.

Al Shabaab, or "The Youth" in Arabic, is known to have recruited foreign fighters from places like Afghanistan, Chechnya, Europe and the US.

But the majority of the group’s foreign recruits come from Kenya, analysts say, drawn from Muslim communities in Eastleigh, the capital’s Somali enclave, and along the coastal strip and arid northeast.

Residents of Eastleigh, which is nicknamed “Little Mogadishu,” told Reuters they fear a backlash following this latest attack.

There is no evidence that ethnic Somalis, or Somali migrants or refugees from Kenya, participated in the attack. But according to Cedric Barnes, Horn of Africa project director for the Brussels-based International Crisis Group, the Somali community in Eastleigh, which has suffered decades of discrimination and neglect, “is a breeding ground for Al Shabaab.”

Barnes says the biggest source of recruitment for Al Shabaab comes from foreign intervention in Somalia.

In August 2011, a 17,700-strong African Union peacekeeping force (AMISOM) pushed the Islamic extremists from the capital. And with help from Ethiopian and Kenyan troops, they routed the militants from towns in southern Somalia in 2012.

Last year, some 4,600 Kenyan troops were stationed in Somalia to help fight the militants.

In statements claiming responsibility for the weekend mall attack, Al Shabaab spokesmen called on Kenya to withdraw its troops from Somalia.

Al Shabaab first emerged in Somalia as the militant wing of the Islamic Courts Union, a group of Islamic law courts that seized power in 2006. They later broke away, and have at various times controlled portions of the country.

According to the US State Department, there were more than three dozen “presumed terrorist incidents” the Kenyan government attributed to Al Shabaab in 2012. But in recent months, the military efforts to defeat the group stalled.

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Here in Kenya, local youth groups, Muslim charities and radical preachers at a spate of new mosques are said to have recruited hundreds of ethnic Somalis and Kenyans for Al Shabaab since 2008.

The Kenyan organization Al Hijra is the movement’s chief recruiter in the country, according to both analysts and the United Nations. It operates through a network of preachers based in Eastleigh’s Majengo slum, where it also fundraises for the movement.

The United Nations Monitoring Group on Somalia and Eritrea, which tracks a regional UN arms embargo, recommended Al Hijra leaders for UN sanctions for their support of the militants.

Al Hijra’s Twitter account frequently calls on Kenyan youth to fight jihad in Somalia and the region, and makes clear its support for both Al Qaeda and Al Shabaab.

But the presence of foreign troops on Somali soil isn't the only driving factor behind high recruitment rates in Kenya.

According to a 2013 report from the Canadian Security Intelligence Service, “the plight of the youth in slums like Nairobi’s Majengo, where Al Hijra was born, is likely to provide a steady flow of recruits.”

Joblessness, poverty and lack of opportunity are common across Kenya. But what makes the Somali community so vulnerable, say young Somalis in Eastleigh, is the mix of increasingly austere forms of Islam and a sense of alienation from wider Kenyan society.

“There are no jobs here. Maybe if you go to fight, you’ll get $300 a month salary,” said Farhan Mohammed, a 24-year-old law student from Eastleigh. “Here, you get nothing. What I know is that the Kenyan government is harassing the community, the Somali people.”

New York-based Human Rights Watch and other rights groups have documented numerous cases of abuse and discrimination against ethnic Somalis in Kenya, who make up about 2 million of Kenya’s 39 million people. Many in Eastleigh see the mass arrests of ethnic Somalis as indiscriminate, racist attacks.

“Without education and employment people think of other ways to survive, and joining extremists is one way,” said Ruun Mohamed, a 27-year old member of the Eastleigh-based organization Youth United for Social Mobilization, a civil society organization. “When they see what the other options are, they start to think of Al Shabaab.”

Those who join are smuggled over the border to Al Shabaab training cramps. Recently, the UN warned that Al Shabaab’s Kenyan fighters could return to carry out attacks at home.

Abdinasir Abdirahman is a 24-year-old preacher at a Sufi mosque in Eastleigh. Sufism is a more moderate, mystical form of Islam that Abdirahman says can counter the growing influence of fundamentalists, who are boosted by wealthy conservative patrons in the Gulf.

“We teach the religion of peace. It is about living happily, living well, not about killing and death,” he said.

In 2011, Abdirahman helped found a youth organization after seeing “youths leave every night for Somalia.”

“So many have joined Al Shabaab,” he said. “Everyone knows someone.”