A suicide bomb attack killed 47 people and injured 79 others as students gathered for Monday morning assembly at their school in north-east Nigeria, police have said.

“There was an explosion detonated by a suicide bomber,” national police spokesman Emmanuel Ojukwu said, referring to the attack in Potiskum in Yobe state.

Survivors told the Associated Press that the bomber was disguised in school uniform and appeared to have hidden the explosives in a type of rucksack popular with students.

Soldiers who attended the scene were reportedly chased away by people angry at the military’s inability to halt a five-year Islamic insurgency that has killed thousands and driven hundreds of thousands from their homes.

About 2,000 students had gathered for the weekly assembly at the Government Technical Science college when the explosion tore through the school hall, according to survivors.

“We were waiting for the principal to address us, around 7.30am, when we heard a deafening sound and I was blown off my feet. People started screaming and running, I saw blood all over my body,” 17-year-old student Musa Ibrahim Yahaya said from hospital, where he was being treated for head wounds.

Hospital workers said dozens were being treated including people with serious injuries who may need amputations.

There was no immediate claim of responsibility for the attack, but Boko Haram militants are likely to be the prime suspects.

The group, which wants to create a hardline Islamic state in northern Nigeria, has previously carried out deadly attacks on schools teaching a “western” curriculum.

In February, gunmen killed at least 40 students after throwing explosives into the dormitory of a government boarding school in Buni Yadi, Yobe state.

In July last year, 42 students were killed when Boko Haram attacked dormitories in a gun and bomb attack on a government boarding school in Mamudo village, near Potiskum.

Boko Haram’s most high-profile attack on a school came in April, when fighters kidnapped 276 girls from Chibok in Borno state, north-east Nigeria. More than six months later, 219 of the girls are still being held.

Potiskum, the commercial hub of Yobe state, has been targeted repeatedly by attacks blamed on Boko Haram. Last week, at least 15 people were killed in a suicide bomb attack targeting a Shia religious ceremony in the city.

Yobe is one of three north-eastern states that has been under a state of emergency since May last year to try to quell the bloody insurgency. But violence has continued and Boko Haram has seized at least two dozen towns and villages in recent months, raising doubts about the government’s ability to control the region.