Three young female suicide bombers detonated explosives -- two of them together at a market in Madagali Monday morning, killing 30 people, a local official said, and one at a checkpoint in Maiduguri, where one person died.
Sunday evening in Maiduguri, Nigerian troops battled armed Boko Haram fighters trying to enter the city, fighting that left at least 21 people dead and 91 wounded, according to Mohammed Kanar, head of National Emergency Management Agency (NEMA).
The Nigerian troops had spotted a group of armed Boko Haram fighters trying to cross a trench to get into the Jiddari Polo area of Maiduguri and opened fire on them, said Babakura Kolo, a vigilante assisting the military in fighting Boko Haram.
That city has been fortified with trenches to prevent infiltration by Boko Haram.
"Some of the insurgents managed to cross into Jiddari Polo and engaged soldiers in battles with guns and explosives," said Usman Bala, another vigilante assisting the military.
Resident Madu Goni said the fighting lasted for almost two hours.
"This forced us to abandon our homes in fear," Goni said.
Hours later, on Monday morning, a teenage female suicide bomber killed one person and wounded seven others in an attack on a checkpoint in the Maiduguri suburb of Kushari, authorities said.
"The suicide bomber blended with the crowd and detonated her explosives," explained a Kushari resident who wished to remain anonymous for fear of Boko Haram reprisals.
Two other residents corroborated his account.
The later attacks in Madagali, with two young female suicide bombers, left 30 dead and at least 16 wounded, according to a local government official who asked not to be named.
Brig. Gen. Victor Ezugwu, the military chief in Adamawa state, confirmed the twin suicide blasts to reporters but gave no further details.
Adamawa state borders Borno state, a Boko Haram stronghold. The militant group has frequently attacked Madagali and in August 2014 briefly captured the town, forcing residents to flee to the state capital of Yola, 225 kilometers south (140 miles).
President: Nigeria has won war against Boko Haram
The attacks came less than a week after President Muhammadu Buhari said in an interview with the BBC
that Nigeria had "technically" won the war against Boko Haram, claiming that the Islamic militant group was no longer capable of launching "conventional, articulated attacks" in towns and population centers.
"Boko Haram as an organized fighting force, I assure you that we have dealt with them," Buhari said.
In October, Buhari gave his military chiefs a three-month deadline to put down Boko Haram. It appears the Islamist group is launching more frequent attacks as the President's December 31 deadline draws closer. Ending the group's insurgency was the backbone of the former military ruler's presidential campaign earlier this year.
A statement from the Nigerian military about the Sunday night fighting framed the situation in a different light, saying that "contrary to earlier media reports and rumors flying around," vigilant military forces intercepted two suspected suicide bombers outside Maiduguri. Those suspects apparently told the military that other suicide bombers were on the way, so "the troops laid ambush on the terrorists' suspected routes ... and eliminated them.
"The suicide bombers were intercepted in three different locations approaching the city," said the statement from Col. Mustapha Anka.
Allegiance to ISIS
In March, Boko Haram pledged allegiance to the Islamic State, and later began calling itself the Islamic State's West Africa Province (ISWAP). Factions in the north of the Sahara and Somalia-based Al-Shabaab have also pledged allegiance to ISIS.
"For ISIS, declaring a 'province' in Africa's most populous country will further perceptions it is on course to achieve its raison d'etre -- creating a unified Islamic State spanning the Muslim world," said Red24 security expert Ryan Cummings.
"Accepting Boko Haram as an ideological proxy also gives (ISIS) an important foothold in a region where prevailing social, political and economic conditions are conducive to religious radicalization," Cummings added.
Thousands have been killed and 1.5 million people displaced since the Boko Haram insurgency began. A recent report named Boko Haram
the deadliest terror group in the world.