LAGOS, Nigeria (AP) — Nigeria faces a shapeless, shifting threat from a radical Muslim sect that has killed more than 100 people in recent days. While the country boasts one of Africa's strongest armies, a military crackdown could drive more supporters into the extremists' ranks.

The U.S. is now warning that the Boko Haram militants may strike next at luxury hotels in the capital of Abuja. Although the military is working to protect such sites, most of Boko Haram's leaders are hiding in neighboring countries and followers easily blend into the population.

The last major government attempt to eradicate Boko Haram in 2009 from this region at the crossroads of Cameroon, Niger and Chad led to hundreds of deaths — and wound up fueling the group's resurgence. The military's efforts to rein in the fighters this year also have prompted complaints of brutality and civilian deaths.

"The government has increased its military presence in northern states and the capital and it's clamping down, but this clamping down has also fueled tensions and I think the government needs to review its own actions to ensure its not exacerbating the situation any further," said Comfort Ero, a Kenya-based analyst for the International Crisis Group.