Residents say two suicide bombers have exploded prematurely in Nigeria's northeastern Maiduguri city, killing themselves and no one else.

The residents blamed Boko Haram, the Islamic State-allied group whose 7-year-old uprising has killed some 20,000 people.

Residents heard two bomb blasts around midnight Sunday, when people were gathering at mosques for special prayers over the holy month of Ramadan. The bombers' shattered bodies were not found until later Monday. Residents spoke on condition of anonymity because they fear angering the military.

There has not been such an attack since troops from Nigeria and neighboring Chad, Cameroon and Niger early this month launched an all-out offensive with daily bombings and a ground offensive.

Nigeria's military said it rescued more than 5,000 Boko Haram hostages in attacks on militant camps this week.