Two female suicide bombers blew themselves up on Tuesday in a crowded market in Nigeria’s north-eastern city of Maiduguri, killing at least 30 people, according to witnesses and a security official.

The two teenage girls entered the busy market and detonated their explosives, said Abba Aji Kalli, the Borno state coordinator of the Civilian Joint Task Force.

The first set off her explosives and killed about three women, said Kalli.

When others gathered around the scene, the second bomber screamed and blew herself up, killing about 30, he said.

“I am right here at the scene and I have before me 11 corpses … many have been taken away by relatives, while others are taken to the state specialists’ hospital,” said Kalli.

Soldiers and police officers cordoned off the area while rescue workers helped survivors to hospital. Nigeria’s police have not yet issued a statement on the incident.

Nigeria’s Islamic militant rebel group, Boko Haram, is suspected of the suicide blasts, as it has carried out similar acts in north-eastern Nigeria. More than 1,500 people have died so far this year in the extremists’ insurgency, according to Amnesty International.

Tuesday’s blast is the first in Maiduguri since 2 July, when 56 people were killed in the same market area as a car bomb went off in group of traders and shoppers.

Maiduguri is the provincial capital and largest city in Borno state, one of the three states in north-eastern Nigeria that are under a state of emergency because of the extremist violence.

In April Boko Haram kidnapped more than 200 schoolgirls from Chibok, about 80 miles south-west of Maiduguri. The schoolgirls remain missing and their plight has aroused international concern.

Last month, on 17 October, their parents were encouraged when the Nigerian military announced a ceasefire with Boko Haram and said negotiations had begun for the release of the schoolgirls.

But those hopes were quickly dashed when Boko Haram fighters continued attacks and seized several cities and towns across the north-east. In a video statement Boko Haram leader Abubakar Shekau denied the ceasefire and scoffed at claims of negotiations to release the schoolgirls.