The Nigerian army says it has killed seven suspected Boko Haram militants during an operation in the Bama area of the northeastern Borno State.

"In simultaneous operations conducted...(in) the area of Bama on Monday, the military recorded huge successes as seven suspected Boko Haram militants were killed and several others injured," regional army spokesman, Mohammed Dole, said on Tuesday.

He said the army has also seized vehicles, explosives and weapons during the raid on militant camps around the flash point area of Bama, where the militants have killed dozens of people in the past week.

On Thursday, some 70 suspected Boko Haram members on motorbikes and pick-up trucks attacked the town of Bama, leaving 27 people dead and destroying some 300 homes.

The group was also blamed for a Saturday attack on a wedding convoy near the border with Cameroon, where gunmen killed more than 30 people, including the groom.

The UN High Commissioner for Human Rights (OHCHR) on Tuesday condemned the "atrocious" attack.

"Members of Boko Haram and other groups and entities, if judged to have committed widespread or systematic attacks against a civilian population - including on grounds such as religion or ethnicity - could be found guilty of crimes against humanity,” OHCHR spokeswoman Cecile Pouilly stated.

In May, the Nigerian government declared a state of emergency in three states in the northeast and launched a campaign against Boko Haram in the area.

Abuja said the militant group has become a security threat in those states.