A bomb attack rocked the Nigerian city of Maiduguri on Tuesday, days after Boko Haram bombings killed 58 people, as the government said the group's allegiance to the Islamic State showed the militants were weakening.
A suspected female suicide bomber blew herself up at the crowded Monday Market, which has been repeatedly hit by Boko Haram attacks, including on Saturday, according to witnesses.
Borno state police commissioner Clement Adoda told reporters that at least seven people died and 17 others were injured in the explosion.
Medical sources said staff were "overwhelmed", as they were still treating some of the 139 people injured in Saturday's blasts.
Mohammed Kanar, the northeast coordinator for Nigeria's main emergency management agency (NEMA) said the authorities successfully carried out a controlled explosion on a second device.
"Another bomb planted... not far from the market was safely destroyed by security operatives. People mistook the explosion for a second attack," he said.
The latest attack came after the government in Abuja described the militants' pledge of allegiance to IS as a sign of weakness in the face of growing military pressure from Nigeria and its allies.
National security spokesman Mike Omeri called it "an act of desperation and comes at a time when Boko Haram is suffering heavy losses".
He added: "Boko Haram is on the way to being eliminated.
"No foreign extremists can or will change this fact -- as long as the Nigerian military continues to receive cooperation and commitment from its citizens and allies.
"There will be no Islamic State in Nigeria, the only state that will exist is the united Federal Republic of Nigeria."
- Coalition gains -
Omeri's tough talk come as Boko Haram is being squeezed out of captured territory in three northeastern states of Nigeria by a regional coalition of Nigeria, Niger, Chad and Cameroon.
The armies have claimed a series of successes in recent weeks, with the operation designed to secure and stabilise the northeast so that elections can take place on March 28.
The Nigerian army said on Tuesday it had foiled a Boko Haram attack on the town of Gombi, in Adamawa state, on Monday evening, seizing heavy weaponry and ammunition.
That followed a Chadian and Nigerien offensive on Monday to retake the Borno state town of Damasak, which fell into rebel hands last November.
Niger said that as of March 8, 24 police and soldiers as well as one civilian were killed since the country became involved in the regional fight-back.
Some 513 Boko Haram fighters were killed in the same period in fighting in southeastern Niger, national police spokesman Adily Toro but there was no independent verification of the numbers.
Security analysts have said Boko Haram leader Abubakar Shekau's pledge of allegiance to his IS group counterpart Abu Bakr al-Baghdadi may only have propaganda value in the short term.
But they did not rule out possible closer links in the future.
Tuesday's bomb attack in Maiduguri -- and a spate of others across the wider north -- have underscored the fragile security in the run-up to the elections, which Shekau has vowed to disrupt.
- Humanitarian crisis -
The Boko Haram conflict, which began in 2009, has claimed more than 13,000 lives and left some 1.5 million homeless, with refugees spread across Nigeria and neighbouring countries.
On Tuesday, the International Committee of the Red Cross warned of an increasingly dire situation for the displaced in the strategic Lake Chad region, where Nigeria meets Niger, Chad and Cameroon.
"There is a full-blown humanitarian crisis around this lake, not only in Nigeria, but also in the surrounding countries," ICRC spokesman Jean-Yves Clemenzo told reporters in Geneva.
The organisation said it had stepped up its efforts in the region, providing food, household items, sanitary facilities and assistance to help cope with the influx of casualties.
But the head of the ICRC delegation in Nigeria, Karl Mattli, said: "It's not enough. More has to be done."
The vast numbers of displaced people -- many of whom have flocked to Maiduguri -- has been a nagging question in the run-up to the vote, at which President Goodluck Jonathan is seeking re-election.
The region is a main opposition stronghold but with many voters unable to return home to cast their ballots, the validity of the overall result may be questioned if they are disenfranchised.
Nigeria's electoral commission is scrambling for a solution to the issue, including temporary voter ID cards.
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