Kano (Nigeria) (AFP) - A child suicide bomber detonated his explosives, killing himself, two other bombers and six people in northeast Nigeria, in the latest bloodshed blamed on Boko Haram Islamist group, the army said on Monday.

The attack in Beninsheikh in Borno state happened around 8:30 pm on Sunday when three suspected suicide bombers aged between 10 and 15 years, were stopped for security screening by civilian vigilantes in the area, Colonel Sani Usman said in a statement.

He said one of the bombers, who was strapped with explosives, detonated the bomb, causing the "death of nine people while 24 others sustained various degrees of injuries."

The three suicide bombers were among the dead, he said.

"The security and emergency management agents have mobilised to the scene. The bodies have been evacuated and all those injured are receiving medical attention," Usman said.

Suicide bombings -- many by young boys and girls -- have fast become Boko Haram's preferred method of inflicting civilian casualties since it lost control of captured territory to a renewed military offensive in recent months.

The defence headquarters said in a statement on Monday that Boko Haram had devised other means of inflicting harm on innocent citizens.

"Some of such tactics they now use include crying and feigning pains and shouting to attract sympathy from the unsuspecting public.

"When a lot of people of goodwill gather to render help in the process, the suicide bomber detonates bombs which they conceal under their clothes," it said.

"Similarly, suicide bombers used monetary incentives and other inducements especially in crowded places to lure innocent citizens in order to cause colossal damage to both lives and property," it said.

It advised Nigerians to be "vigilant and weary of terrorist malevolence in such places as parks, worship centres and recreation spots particularly in this festive period.".

People were also advised to report suspicious movements to the security agencies.

Nigeria's President Muhammadu Buhari has given his military commanders until the end of the month to end the six-year violence.