Hundreds of Kenyan youths who converted from Christianity to Islam—and then went to fight alongside jihadists in neighboring Somalia—are returning to their home churches. But these prodigal sons are not being welcomed back with fully open arms.

Instead, pastors are on high alert—with good reason. Al Shabab, an al-Qaeda affiliated militia, has begun using young men from predominantly Christian ethnic groups to attack churches.

In November, an assailant hurled a grenade into a church located inside a police station, killing the pastor. In September, assailants threw grenades into a children's Sunday school class, killing a 9-year-old boy. In July, similar grenade attacks at two churches killed 17 worshipers.

Last October, Kenyan military forces entered Somalia to engage Al Shabab. The militia responded with a recruitment drive of Kenyan youth, offering cash incentives for the families of would-be martyrs.

"[Jihadists] have changed their recruitment tactics," said Wellington Mutiso, head of Evangelical Alliance of Kenya. "Instead of enlisting from predominantly Muslim communities such as the Somali, Boran, and others, they are targeting those from tribes that are majority Christians, such as the Kikuyus, Luos, and Luhyas."

Mutiso believes this is "an act of disguise," given that security forces have been concentrating on suspects from Muslim communities. "With the new recruits, the security forces have been left in a spin."

Jihadists have an easier time recruiting within Christian communities today because of Kenya's high unemployment rate (40 percent) and widespread poverty.

"A member of my church was given 50,000 Kenyan shillings (us$570), and he immediately converted to Islam," said David Gathanju, head of the Presbyterian Church of East Africa. "There is also the issue of young men looking for quick money and not wanting to soil their hands in hard work."

That's what worries Mutiso. Former church members who fought in Somalia can attribute their absence to going away to college or changing jobs to a different town, he said. "They are less likely to be under close scrutiny and, before you know it, they will have wreaked havoc."

After a joint African military operation dealt Al Shabab a significant blow in October, capturing the jihadist coastal stronghold of Kismayu, the militia moved its fight onto Kenyan soil.

This has resulted in a disturbing increase in Nigeria-style attacks on churches, forcing leaders to increase security. Nowadays it is common for churchgoers to be frisked and have their cars checked for explosives. Armed policemen have become part and parcel of almost all Kenyan church services.

In October, Alex Shikinda (now known as Musharaf Abdalla) became the latest convert from Christianity to confess in court to handling explosives on behalf of Al Shabab. In late 2011, another Kenyan from a western Christian tribe, Elgiva Bwire Oliacha (now known as Mohammed Seif), pleaded guilty to grenade attacks in Nairobi.

For Mutiso, the solution to this problem lies squarely with the government. "They know the mosques that were used as recruitment grounds," he said. "They can get information from the sheikhs [regarding who was recruited], so we can circulate the information among churches."

Another solution: Offer amnesty to those who renounce their conversion to radical Islam. Mutiso acknowledges it would be hard to distinguish between a genuine amnesty seeker and a fake one bent on attacking former brethren. "But desperate times call for desperate measures," he said. "We need to try all possible solutions."

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