DAKAR, Senegal — Suicide bombers killed at least 30 people and injured dozens more in northeastern Nigeria late Sunday, unleashing the deadliest blasts this year in a region plagued by extremist violence.

Two girls and a boy, all teenagers, detonated explosives in a tea hall where people had gathered to watch soccer in the small town of Konduga, authorities said.

No group immediately claimed responsibility for the attack, which copied a tactic used by Boko Haram, the terrorist organization that has tried in the past decade to build a radical Islamist state in the country. 

Nigerian President Muhammadu Buhari says Boko Haram has been defeated. But analysts say the militants have maintained a stubborn grip on Borno state, where violence has claimed hundreds of lives in recent months. 

Nigeria, Africa’s most populous nation, faces widespread security threats, with militant Islamist insurgencies persisting in the northeast as clashes continue to the south between farmers and herders. Government corruption hinders efforts to ease conflict, analysts say, siphoning off resources that could be used in the push for peace. 

“It’s not accurate to say Boko Haram has been technically defeated,” said Isa Sanusi, spokesman for Amnesty International in the Nigerian capital, Abuja. “Boko Haram is still vicious.”

The conflict is growing more complicated, Sanusi said, as the Islamic State of West Africa ramps up attacks along the Lake Chad basin, striking mostly military personnel. Boko Haram targets civilians.

Boko Haram, which means “Western education is forbidden,” is known for sending suicide bombers, particularly women and children, into crowded markets, bus stations and mosques. Female assailants tend to follow a disturbing pattern, according to reports: They apply makeup, wear loose clothing and strap bombs to their waists.

The group grabbed international attention five years ago after kidnapping hundreds of schoolgirls in the town of Chibok. More than 100 are still missing.

An estimated 37,000 people have died in the violence since 2011, according to the Council on Foreign Relations’ Global Conflict Tracker

Attacks have dropped off since the Nigerian military — with help from Benin, Cameroon, Chad and Niger — shrank Boko Haram’s operating terrain. But the group still holds some villages in the northeast, making remote places such as Konduga especially vulnerable. 

The last suicide attack in the region happened in April. Two women detonated devices near the village of Monguno, killing a soldier and a man who tried to stop them. 

During Nigeria’s presidential election in February, gunmen and suicide bombers killed eight people in the city of Maiduguri.

Konduga, where roughly 13,400 people live, has for years grappled with suicide bombers from a faction of Boko Haram led by Abubakar Shekau, who has embraced indiscriminate violence in his quest for territory.

Eight people died there last July after a suicide bomber entered a mosque.

The Sunday blasts, which injured 47, erupted on the same day that an armed gang killed 34 people in the northwestern state of Zamfara. Police blamed that attack on bandits.

Extremist groups in northeastern Nigeria used 48 children, mostly girls, in suicide bomb attacks last year, according to UNICEF.