MAIDUGURI, NIGERIA: Boko Haram Islamic extremists struck the northeastern Nigerian city of Maiduguri for the first time in months Monday with rocket-propelled grenades and multiple suicide bombers, witnesses said. At least 50 people were killed and the death toll could go higher.

At least 30 were killed and more than 90 wounded in overnight blasts and another 20 were killed at Monday's mosque bombing, said Muhammed Kanar, coordinator for the area's emergency agency.

The military said there were multiple attacks at four southwestern entry points to the city, including a woman suicide bomber who killed one other person and injured 13 gathered outside a mosque after dawn prayers Monday.

In another blast, two girls blew themselves up in Buraburin neighborhood, killing several people, according to civil servant Yunusa Abdullahi.

"We are under siege," Adullahi said. "We don't know how many of these bombs or these female suicide bombers were sneaked into Maiduguri last night." He said some residents have found undetonated bombs.

The attack appears to be a challenge to President Muhammadu Buhari's declaration last week that Boko Haram has been "technically" defeated, capable of no more than suicide bombings on soft targets.

Acting on information provided by a captured insurgent, Nigerian troops "intercepted and destroyed" 13 suicide bombers and arrested one female suicide bomber in repelling the attackers, Maj. Gen. Lamidi Adeosun, the commander prosecuting Nigeria's war against Boko Haram, told reporters.

Maiduguri, the city under attack, is the birthplace of Boko Haram, which emerged as a much more radical entity after Nigerian security forces launched an all-out assault on their compound in the city, killing 700 people in 2009.

Militants firing indiscriminately from the back of three trucks attacked the outlying village of Dawari, soldiers engaged them, and as people were fleeing, a woman ran into the area yelling "Boko Haram, Boko Haram." When people gathered, she detonated herself, according to village head Bulama Isa.

A rocket-propelled grenade then exploded, setting alight grass-thatched huts, and a second woman blew herself up, according to Isa. Among those killed was the village chief and 10 of his children, according to residents Ahmed Bala and Umar Ibrahim.

A soldier said the insurgents fired rocket-propelled grenades into four residential areas on the outskirts of the city. Soldiers fired back, and many civilians were caught in the crossfire, according to the soldier, who spoke on condition of anonymity because he is not authorised to speak to journalists.

Three suicide bombers blew themselves up at a home near Bakassi Estate, killing 18 people Sunday evening, another soldier told The Associated Press.

A nurse at Maiduguri Specialist Hospital said dozens of critically wounded, mainly children and women, may not survive. The nurse, who spoke on condition of anonymity because she is not authorised to speak to reporters, said the hospital was so overflowing with patients that some had to be cared for in the maternity ward. About 60 people had wounds from bullets and shrapnel from explosive devices, she said. Other wounded people had to be sent to other hospitals in the city.

Among them was a baby found dead, still tied to the back of her mother, who survived after being hit by shrapnel, the nurse said.

It was hard to do a body count because so many had been blown into pieces, she said, describing torsos and dismembered arms and legs.

Maiduguri, a city of about 1 million people, now hosts almost as many refugees, among 2.5 million people driven from their homes in the 6-year-old uprising. About 20,000 people have been killed in Nigeria and hundreds others elsewhere as the insurgents have carried their conflict across its borders into Cameroon, Niger and Chad.