Suicide bomb attackers killed 10 people and wounded 30 in the northeast Nigerian city of Maiduguri on Wednesday, an emergency agency official said.

Axar.az reports citing Reuters that Islamist militant group Boko Haram has killed more than 20,000 people since 2009 as part of its attempt to create an Islamic state in the Lake Chad basin.

No one immediately claimed responsibility for the latest attack, which emergency officials and members of a government-approved vigilante group said was carried out by four female bombers in the Muna Garage district of Maiduguri at about 06:00 p.m. (1700 GMT).

The use of female bombers is a hallmark of Boko Haram attacks.

“We have so far recorded 10 people’s deaths and about 30 victims injured,” said Bello Dambatta, a spokesman for the State Emergency Agency (SEMA).

Maiduguri is the capital of Borno state and the city worst hit by the jihadist insurgency. At least 221 people have been killed in bombings and gun attacks in northeast Nigeria since June, according to a Reuters tally.