Two children, both girls have been were strapped with explosives which exploded in a Nigerian market.
A trader at the market in the town of Potiskum in the northeast Yobe state said the bombers were about 10 years old.
Another witness said two ambulances had arrived on the scene this afternoon and were picking up corpses.
The number of casualties from today's bombings is still unclear.
Yobe state is frequently attacked by Boko Haram.
Earlier, Nigeria's military called for support in tackling Boko Haram after a major attack on a key northeast town that is feared could be the worst in the bloody six-year insurgency.
There are still no independently corroborated figures for the huge numbers said to have been killed in Baga, on the shores of Lake Chad in the far north of Borno State.
However, defence spokesman Chris Olukolade said in a statement issued the description of the assault as "the deadliest" was "quite valid".
Yesterday, a young girl strapped with explosives was involved in a similar attack in the northeast Nigerian city of Maiduguri.
19 people were killed.
Borno State police spokesman Gideon Jubrin told reporters: "Casualty figure: 20 dead and 18 injured, including the female suicide bomber that detonated the improvised explosive device."
The blast happened at about 12.40pm (11:40am Irish time) near the live chicken section of the Monday Market in the Borno State capital, which was targeted twice in a week by female bombers late last year.
Nigeria's military, West Africa's largest, has faced repeated criticism for failing to end the six-year Islamist insurgency, as well as allegations of human rights abuses.
Soldiers have complained of a lack of adequate weapons and even refused to deploy to take on the better-armed rebels, who want to create a hard-line Islamic state in northeast Nigeria.
With elections set for next month, Nigeria's government has also been accused of playing politics with the insurgency, as most of the areas worst affected by the violence are main opposition strongholds.
But Mr Olukolade said: "The Nigerian military has not given up on Baga and other localities where terrorist activities are now prevalent.
