At least 21 people were killed in two separate Boko Haram attacks on villages near the key city of Maiduguri in northeast Nigeria, a community leader and a witness said on Friday.

At least 21 people were killed in two separate Boko Haram attacks on villages near the key city of Maiduguri in northeast Nigeria, a community leader and a witness said on Friday.

"They (Boko Haram) killed 12 people in Akida village and nine others in Mbuta village during a raid," said community leader Mustapha Abbagini.

A witness to the attack in Mbuta gave the same death toll while both said that the insurgents destroyed shops and homes in the raids, which happened on Thursday morning.

The two attacks came before a female suicide bomber blew herself up at a crowded market in the town of Biu, in the south of Borno state, of which Maiduguri is the capital.

A civilian vigilante helping the Nigerian Army in the counter-insurgency and a source at the town's hospital both said that the death toll had risen from seven to 11 after the blast.

"Four more people, all of them adults, died at the hospital here in Biu while receiving treatment," said the vigilante, Abor Kabiru.

A source at Biu General Hospital added: "Four of the victims brought here with injuries died at night and so far, at least 11 dead bodies have been identified."

The death toll could increase further, as health officials were working to establish the identities of at least two other people who were blown apart by the strength of the blast.

The source asked not to be identified because they were not authorized to speak to the media.

"There are still about 13 victims who are receiving treatment while seven others with less severe injuries have been treated and discharged," the source added.

The attack in Akida, which is some 25 kilometers (16 miles) from Maiduguri, happened at about 4:30 am (0330 GMT) when villagers were asleep, said Abbagini.

After setting homes and businesses on fire, the insurgents left and attacked Mbuta at about 7:25 am, he added.

Mbuta resident Hamidu Bukar said: "The attackers destroyed about 25 houses and five shops in our village after killing nine people that attempted to flee from their assault.

"The attackers came from (the) Dikwa area (of Borno state) and they accused us for spying for military authorities... I don't know what they mean by that.

"They threatened that if they fail in their future operations of advancing towards Maiduguri, they would destroy our villages."