Updated

Military officials say they have uncovered mass graves of decomposing bodies, networks of underground tunnels and caches of buried arms in raids that killed dozens of Islamic extremists in Nigeria's northeastern city of Maiduguri.

Sunday's statement about last week's raids contradicts previous military assurances that it had forced militants out of major cities and towns in a two-month-old security crackdown in three northeastern states covering one-sixth of Nigeria.

Spokesman Lt. Col. Sagir Musa said security forces also rescued many women and girls kidnapped by the extremists in an attack in Maiduguri's Bulabulinganaram neighborhood.

The extremists are alleged to be part of a group known as Boko Haram, which is believed responsible for hundreds of deaths and opposes education it deems as being "Western."