Two female child suicide bombers blew themselves up on Sunday in the northeastern Nigeria town of Potiskum, a day after a 10-year-old girl reportedly killed at least 19 people in the Borno State capital of Maiduguri in another suicide attack.

The Islamist group Boko Haram is suspected of orchestrating the Sunday bombings, which killed at least six people. The fact that young girls were used in the attacks has raised questions about whether the militants are weaponizing the 273 schoolgirls they kidnapped from a secondary school in Chibok in April 2014. Some of the young female captives managed to escape, but around 230 remain unaccounted for.

In December, a suspected Boko Haram suicide bomber, who was captured at the entrance to the University of Maidiguri, reportedly said the militant group had deployed more than 50 female suicide bombers in the city. That foiled attack came after a series of market suicide bombings carried out by females in Maidiguri during November that left more than 90 people dead.

'There is a very real possibility that the girls who haven't been killed or sold are being used.'

At the time, terrorism and insurgency experts disagreed over whether the Chibok girls were used in the suicide bombings. None of the female suicide bombers used by Boko Haram have been positively identified as coming from Chibok.

Hilary Matfess, a researcher at the Nigeria Social Violence Project (NSVP) at Johns Hopkins University, told VICE News that despite the uncertainty, it was notable that every female suicide bombing tallied by the project occurred after the Chibok kidnappings.

"There is a very real possibility that the girls who haven't been killed or sold are being used," Matfess said.

The NSVP has recorded some 12,000 deaths caused by violence tied to Boko Haram in recent years, and says the fatalities have risen at a greater pace in the past several months.

A series of Boko Haram attacks in Baga and several nearby towns in Borno State last week resulted in heavy civilian casualties. In Baga, militants first targeted a military installation before turning their weapons on locals who were unable to flee. The BBC reported local defense groups had given up counting the bodies of the attack, quoting a spokesperson for one of the group as saying that "no one could attend to the corpses and even the seriously injured ones who may have died by now."

On Monday, the Nigerian government said earlier estimates that put the death toll as high as 2,000 were "exaggerated" and claimed the number of dead was no higher than 150 in Baga. Nigerian security forces are said to be attempting to retake the town.

The UN says the recent violence in Borno State has forced 7,300 people to flee into neighboring Chad, where they have required humanitarian aid.

Cameroon, whose army is also involved in fighting Boko Haram along the border with Nigeria, said the country's troops killed 143 fighters after the militants attacked a base Monday in the town of Kolofata, according to AFP.

'These images of recent days and all they imply for the future of Nigeria should galvanize effective action, for this cannot go on.'

The killings in Borno coincided with an outpouring of support for the victims of terror attacks that occurred last week in France. Over a million people — including an array of world leaders — attended a unity rally on Sunday in Paris.

On Monday, a high-ranking Nigerian Catholic official said that world leaders ought to offer similar shows of support for Boko Haram's victims in Nigeria.

"We need that spirit to be spread around, not just when it happens in Europe, (but) when it happens in Nigeria, in Niger, Cameroon, and many poor countries," Ignatius Kaigama, Archbishop of Jos in central Nigeria, told BBC World Service radio.

Kaigama made his remarks after UNICEF Executive Director Anthony Lake said the use of young girls in suicide attacks "should be searing the conscience of the world."

"These images of recent days and all they imply for the future of Nigeria should galvanize effective action, for this cannot go on," Lake said on Sunday.

The continued violence in northeast Nigeria comes as three northern states — Adamawa, Borno, and Yobe — remain under a state of emergency only a month before the country's presidential election. The hard-fought contest pits incumbent Goodluck Jonathan against rival Muhammadu Buhari and it has the potential to further wrench the country apart, particularly if voting is disrupted in parts of the three states.

Buhari and others routinely criticize Jonathan for overseeing what many consider a botched intervention against Boko Haram, which took up arms against the government in 2009. Last week, Jonathan issued a statement calling the events in Paris a "dastardly terrorist attack," but remained largely mum about the recent suicide attacks.

The political implications of Boko Haram attacks are difficult to parse. Some believe an uptick in bloodshed — and increased coverage of the ease with which militants penetrate cities and towns — could hurt Jonathan's chances for re-election.

Buhari issued a statement on Saturday on the recent violence. "Nigeria has become a place where people no longer feel safe, where the armed forces have neither the weapons nor the government support required to do an effective job of protecting Nigerian citizens and their property," he said.