Poor, jobless Somalis are tempted by promises of $600 (£374) a month
By Jenny Cuffe
BBC World Service
Two hundred kilometres of desert scrubland populated by nomads herding camels and goats lie between Garissa and Kenya's border with Somalia.
Around the corrugated-iron shelter where women sell milk each morning from yellow plastic drums, conversation focuses on the encroachment of warring militia and the recent victories of al-Shabab, an Islamist group accused of links to al-Qaeda.
Although the Kenyan government has sent troops to guard the border, people in this region fear that the rebel group has already infiltrated Kenya and is recruiting vulnerable youngsters.
As ethnic Somalis, there is nothing to distinguish the insurgents from their Kenyan neighbours.
Hassan Sherie, who runs an organisation helping unemployed youth, believes they have a sophisticated network of operatives with links to some Koranic schools in Garissa.
He does not think their fundamentalist ideology will attract young Kenyans but says they use generous sums of money as bait.
It was the offer of $600 (£374) a month that persuaded Abdullah (not his real name) to join.
He was in a group of 20 young men recruited in 2008 at a mosque in Garissa.
"We were jobless. That's what encouraged us to join al-Shabab," he says.
"We were told we were fighting a holy war, a jihad, and if you kill supporters of the government you will go to heaven."
He and his friends were taken across the border where Arab trainers taught them how to use AK47s and bazookas.
After two months, they were sent to the southern Somali port of Kismayo and ordered to disarm civilians.
Abdullah says al-Shabab was attacking local Somalis rather than infidels and he was frightened by their brutality.
"They were praying and reading the Koran but doing evil things," he says.
"I witnessed four men having their hands chopped off and people in captivity were very scared."
When his commanders stopped paying him, he decided to leave, returning to Garissa last autumn.
He thinks some of his friends are still fighting with al-Shabab in Somalia.
Many civic and religious leaders blame their own government for driving young people into the arms of the rebels.
In October last year, 300 young men were recruited to fight for al-Shabab's enemy - Somalia's UN-backed transitional government, and sent to Manyani, a training school in Tsavo National Park, where they say they were instructed by Kenyan soldiers.
The Kenyan government denied responsibility for the recruitment but, after a protest from parents and elders, most of the Kenyan Somalis were sent home.
Now, men like 20-year-old Abdi find themselves back on the street with no employment and no hope for the future. He describes himself as a trained soldier and says he would be open to an offer from al-Shabab.
"I'll go and fight for them because what I'm looking for is money," he says.
'This is your war'
According to Garissa mayor Mohammed Gabow there is a strong chance that men like Abdi will use their military training to harm their fellow citizens.
They used to think that the fighting in Somalia was not their business but that has changed.
"You have people being told that, after all, this is your war and it is dangerous."
Al-Shabab does not confine its activities to Kenya's frontier province.
In Eastleigh - a district of the capitol Nairobi known as "Little Mogadishu" because of the number of Somali refugees - the BBC was able to obtain a recording of an imam urging youngsters to join al-Shabab and fight the infidels.
It is a message relayed behind security gates at a makeshift mosque on the Ushirike Estate.
Although Kenya's assistant Defence Minister General Joseph Kaiseri acknowledges the risk of infiltration, he says the government's intelligence and anti-terrorism systems are sufficient to counter any threat from al-Shabab.
Independent analysts, however, are not so sure.
Rashid Abdi, Somalia expert for the International Crisis Group (ICG), believes lax security and corruption make it an ideal place for the Islamist group to raise money and recruit.
"What will stop an al-Shabab person operating in Kenya?" he asks.