Nigerian soldiers backed by air support have tracked down and killed 50 members of Islamist sect Boko Haram in the sect’s northeastern stronghold, an army spokesman said on Saturday, Sept 7, according to Reuters.

Boko Haram, which wants to impose sharia law in northern Nigeria, and other splinter Islamist groups, are the biggest threat to stability in Africa’s top oil exporter.

A concerted military crackdown on Boko Haram ordered by President Goodluck Jonathan in mid-May had appeared to have weakened the sect, but they have repeatedly proved masters at going into hiding then coming back just as deadly as before.

On Sept 2, Islamists in Nigeria ambushed a minibus, ordered passengers to exit, and then shot those that were Christian. They were ordered to lie down on the side of the road and were executed. Those killed ranged in age from 22 to 40.

About 88,000,000 Nigerians are Muslims, approximately 50% population of Nigeria. Muslims in Nigeria are predominantly Sunni in the Maliki school, which is also the governing Sharia law.