By PETER WONACOTT

Somali militia

Al-Shabaab Uses Videos, Financial Incentives and Brute Force to Draw Members

EASTLEIGH, Kenya—When Islamic militants came for Qassim Mohamed, the Somali self-defense coach couldn’t defend himself.

The men from al-Shabaab, the al Qaeda-backed group that claimed responsibility for the deadly Nairobi mall attack, beat the karate instructor as they tried to recruit him. They slammed rifle butts into his chest and threatened to kill his family. Mr. Mohamed didn’t dare raise a fist. Instead, family members paid bribes for his release and he fled the capital Mogadishu to Kenya in 2009.

“If you try to defend yourself, you will die,” said Mr. Mohamed, now 30 years old, who counsels other Somalis against extremism as part of a new youth mentor program in Eastleigh, outside Nairobi. “I escaped, started a new life, but al-Shabaab will always be behind me.”

From the strife of Somalia to the slums of Kenya to the leafy streets of Minneapolis, Minn., al-Shabaab has put together a global recruiting network to replenish its militancy. The drive draws on videos for the curious; small financial incentives for the poor; and sometimes brute force for the reluctant, said people who have had contact with members of the group.

The common trait among them, say analysts and aid workers, is a willingness to kill for their religion.

“Looking for a socio-economic profile to who al-Shabaab recruits would be less useful than looking for a psychological profile,” said Cedric Barnes, Horn of Africa director for the International Crisis Group.

A spokesman for al-Shabaab didn’t immediately respond to an email seeking comment about its recruiting efforts. The al-Shabaab militancy, which sprung from Somalia’s two-decade civil war and vowed allegiance to al Qaeda last year, has become a growing regional threat.

It carried out multiple blasts in July 2010 that struck Kampala, Uganda, killing more than 70 people who were watching the World Cup soccer finals. In Somalia, al-Shabaab recently hit a number of civilian targets, including the United Nations compound and the country’s Supreme Court. It also took responsibility for the shooting rampage that began Saturday at the popular Westgate mall in Nairobi that left more than 60 people dead, Kenya’s biggest terror attack since the U.S. Embassy bombing in 2008.

On Thursday, forensics experts with the Federal Bureau of Investigation, Interpol and a number of other countries combed through the wrecked interior of the shopping center. Police on the scene said no additional bodies were pulled out during the day.

Kenyan officials said the al-Shabaab mall attackers represented multiple countries, and may have included Americans and a British woman. An international arrest notice was issued Thursday for Samantha Lewthwaite, a British woman who is the widow of one of four London suicide bombers who killed 56 people in 2005. The Kenyan government is investigating the 29-year-old Ms. Lewthwaite in relation to the Nairobi attack; she is also wanted on explosives-related charges tied to a 2011 terror plot.

Ms. Lewthwaite, who is believed to have come to Kenya in 2011, is among a number of Westerners who authorities say have joined the Somali militancy in recent years. A 2011 report from the U.S. House Committee on Homeland Security found at least 40 Americans have joined al-Shabaab. Kyle Loven, spokesman for the FBI in Minnesota, said his office has had an active investigation since 2007 into so-called travelers who have left Minnesota—which has the largest population of Somali-Americans in the U.S.—to engage in terrorism activities in East Africa. Mr. Loven said federal authorities recently discovered videos that seek to entice Somali-Americans to join the group by glamorizing fighting in Somalia. He said he wasn’t able to confirm whether Minnesotans were involved in the Nairobi mall attack.

The best-known American member of al-Shabaab was Omar Hammami, an Alabama native who rapped and tweeted on behalf of the group. Mr. Hammami, nicknamed “the American” among fellow militants, is believed to have been killed in recent al-Shabaab infighting.

But it is the refugee camps and slums of Kenya that provide the most constant flows of al-Shabaab recruits outside Somalia. The country has about 500,000 Somali refugees in a camp on its northeastern border with Somalia. More than two million Somalis live in Kenya. Al-Shabaab has stepped up attacks in Kenya after the government in 2011 dispatched troops to Somalia to drive militants from strongholds.

Al-Shabaab also claimed responsibility for an attack Wednesday night on a police station in northeast Kenya that killed two officers. The Kenyan government said it has now beefed up security in towns along the Somalia border. The group’s leader said late Wednesday that there is no way Kenya can “withstand a war of attrition inside your own country.”

In a statement posted online, Ahmed Abdi Mohamed Godane, who goes by his nom de guerre Mukhtar Abu Zubayr, said, “Make your choice today and withdraw all your forces. Otherwise be prepared for an abundance of blood that will be spilled in your country, economic downfall and displacement.”

In Eastleigh, known as Little Mogadishu for its many Somali refugees, there is widespread fear the Nairobi attack will intensify police scrutiny. At the same time, the Nairobi slum has been a frequent target of grenade attacks blamed on al-Shabaab. The tensions have created a market for mental-health professionals and a man who walks through Eastleigh’s muddy streets selling plastic posters of kittens that read: “Peace for a Troubled Mind.”

Dr. Maimuna Mohamud, who helps run a local health clinic with her husband, said there has been a surge in Somali patients with stress-related symptoms since the mall attacks. “We fear the police. We fear al-Shabaab,” she said.

Police spokeswoman Zipporah Mboroki said they have “an open-door policy” to combat extremism in communities. “If anyone has information they can report it to the police,” she said.

Al-Shabaab is drawing recruits beyond Little Mogadishu. In Majengo, a slum for poor Kenyans, small mosques are popping up between corrugated shacks. In a place where most people don’t have work, local mosques often ease financial hardship, subsidizing weddings and offering free burials for the dead, said Robert Ochona, a local radio journalist.

Collins Andago, a 25-year-old car washer in Majengo, said his brother, Musa, became a recent convert to Islam and then suddenly disappeared in 2011. Collins Andago reported his brother to Kenya’s counterterrorism police, who tracked him to Mombasa, where he and another friend were trying to get to Somalia. The friend made it to Somalia, he said.

Musa Andago, 19, is now back home but declined to be interviewed. Collins Andago estimates more than 100 young men from Majengo have headed to Somalia over the past couple of years.

“They think you fight jihad you will go to heaven,” he says. “They go and don’t come back.”

Mr. Mohamed, the karate coach, has stayed away from Somalia, but al-Shabaab has continued to menace him. Group members have dropped by the family home in Mogadishu to ask where he is. His father would profess not to know. In April, a group of three men shot and killed his father as he walked home from the mosque, Mr. Mohamed said.

The choice for al-Shabaab is simple, he says. “To be with them. Or to die.”