Islamist extremists from Boko Haram struck a city and a town in northeastern Nigeria with rocket-propelled grenades and multiple suicide bombers Monday, killing at least 80 people, witnesses said.

In Maiduguri, the capital of Borno state, at least 30 people were killed and more than 90 wounded in overnight blasts and shootouts, and 20 died in a bombing outside a mosque at dawn Monday, said Muhammed Kanar, area coordinator for the National Emergency Management Agency.

Twin suicide bombings killed at least 30 people in Madagali, a town 95 miles southeast of Maiduguri, witnesses said.

The attacks appear to be a challenge to President Muhammadu Buhari’s declaration last week that security forces have “technically won the war” against Boko Haram and that the Islamist militant group is now capable of no more than suicide bombings aimed at soft targets.

Maiduguri, with a population of about 1 million, now hosts almost as many refugees — among the 2.5 million people driven from their homes in the six-year-old Islamist uprising. About 20,000 people have been killed in Nigeria and hundreds more elsewhere as the insurgents have carried their conflict into Cameroon, Niger and Chad, which are part of a regional force fighting Boko Haram.

Nigeria’s military said there were multiple attacks at four southwestern entry points to Maiduguri.

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

“We are under siege,” Abdullahi 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.

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

Acting on information provided by a captured insurgent, Nigerian troops “intercepted and destroyed” 13 would-be suicide bombers and arrested one female would-be suicide bomber, Maj. Gen. Lamidi Adeosun, the commander prosecuting Nigeria’s war against Boko Haram, told reporters.

Soldiers arrested seven Boko Haram bomb specialists, according to PRNigeria, which issues government statements.

A nurse at Maiduguri Specialist Hospital said dozens of critically wounded victims, mainly children and women, may not survive.