At least 13 people are dead, including four attackers, after Boko Haram launched the deadliest attack in months on the northeast Nigeria city that is the birthplace of the extremist group, police said Thursday. The attack came just hours before a visit by the country's acting president.

Nigeria late last year declared that Boko Haram had been crushed but attacks continue, often with young women strapped into explosives for suicide attacks.

The militants attacked late Wednesday in Maiduguri, the capital of Borno state, as evening prayers were ending, targeting four locations around the city. Thirteen people were killed, including four attackers, Police Commissioner Damian Chukwu said.

Extremists also clashed with soldiers outside the city in Alidawari village and Jiddari Polo suburb, where homes were set on fire, Chukwu said. Nigerian forces killed three Boko Haram insurgents in that fighting, he said, and one attacker was captured alive.

Acting president Yemi Osinbajo arrived in Maiduguri on Thursday to launch a food relief program for hundreds of thousands of people who have fled their homes in the wake of Boko Haram attacks in the region.

The eight-year insurgency has killed more than 20,000, kidnapped thousands and spilled into neighbouring countries, creating a vast humanitarian crisis with thousands said to be near starvation.

The attacks late Wednesday in Maiduguri took place in various locations around the Chad Basin Development Authority headquarters just before 9pm, resident Alhaji Bashir said. The targets included a mosque, he said.

Young members of a civilian defence group, who have come together to combat the extremists, saw one suicide bomber at the headquarters.

“One of the youth vigilantes rushed to hold him, and the bomb went off and killed the suicide bomber and three other persons,” Bashir said.

In another attack, a female suicide bomber entered a crowd of worshippers leaving prayers and detonated her explosives, he said.

Dozens of injured people filled the University of Maiduguri Teaching Hospital on Thursday, said Abba Shehu, a private security worker.

“It is a horrible sight we have here,” he said. "I could not count the number of injured casualties at the accident and emergency ward, most of them sitting on the floor as the place is crowded and no beds to properly admit them."