The two women yesterday targeted a crowded market in Potiskum, Yobe State, a day after 19 people were killed in a similar attack in neighbouring Borno State, by a girl thought to be aged just 10.
Potiskum -- a repeated target for the militants -- was also hit on Saturday, when a car exploded outside a police station, killing the driver and an officer.
The three explosions followed what is thought to be the worst attack in the bloody six-year insurgency, when Boko Haram fighters attacked the Borno town of Baga and razed at least 16 surrounding settlements.
"The attack on the town by the bloodhounds and their activities since January 3rd, 2015, should convince well-meaning people all over the world that Boko Haram is the evil all must collaborate to end, rather than vilifying those working to check them," said defence spokesman Chris Olukolade.
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Nigeria's military -- west Africa's largest -- has faced repeated criticism for failing to end the Islamist insurgency, as well as allegations of human rights abuses.
In Baga, 14 soldiers were killed, Olukolade said, but independent corroboration of the huge numbers of dead cited locally has so far been impossible to obtain.
The UN children's fund said harrowing reports from survivors of the attack and the use of a 10-year-old girl as a human bomb in Borno state capital Maiduguri "should be searing the conscience of the world".
"Words alone can neither express our outrage nor ease the agony of all those suffering from the constant violence in northern Nigeria," UNICEF executive director Anthony Lake said in a statement.
Boko Haram, which has been fighting to create a hardline Islamic state in northeast Nigeria, has in the last six months seized dozens of towns and villages in the remote region, seemingly at will.