Suspected Boko Haram militants using young girls as suicide bombers killed 31 people in an attack on a town in northeast Nigeria, a local official and a militia leader told AFP on Sunday.

Blasts ripped through the town of Damboa in Borno state on Saturday evening targeting people returning from celebrating the Eidul Fitr holiday, in an attack bearing all the hallmarks of Boko Haram.

Following the suicide bombings, the militants fired rocket-propelled grenades into the crowds that had gathered at the scene of the attacks, driving the number of casualties higher.

“There were two suicide attacks and rocket-propelled grenade explosions in Damboa last night which killed 31 people and left several others injured,” said local militia leader Babakura Kolo.

The suicide bombers detonated their explosives in Shuwari and nearby Abachari neighbourhoods in the town around 10:45 pm (2145GMT), killing six residents, said Kolo, speaking from the state capital Maiduguri, which is 88 kilometres (55 miles) from the town.

“No one needs to be told this is the work of Boko Haram,” Kolo said.

A local government official, who spoke on the condition of anonymity, confirmed the death toll.

“Most of the casualties were from the rocket projectiles fired from outside the town” after the bombings, he said.

“It was later realised the suicide attacks were carried out by six underage girls whose decapitated heads were found at the scene by rescue teams.

They were between seven and 10 years, from their looks,” said the official.

The gruesome attack is the latest example of Boko Haram's continued threat to Nigeria and the Lake Chad region, said Ryan Cummings, Africa analyst at the Signal Risk consultancy in South Africa.

“Boko Haram still maintains both the intent and operational capacity to launch mass casualty attacks in parts of northeastern Nigeria,” Cummings said, despite the government's repeated claims that the group is on the back foot.

The use of the rockets is “particularly conspicuous,” Cummings said, as it “indicates that the sect continues to have access to military-grade weaponry.”

“The Boko Haram insurgency is not showing any immediate signs of easing,” said Cummings.

Suicide bombings -

The militant group has regularly deployed suicide bombers — many of them young girls — in mosques, markets and camps housing people displaced by the nine-year insurgency.

On May 1 at least 86 people were killed in twin suicide blasts targeting a mosque and a nearby market in the town of Mubi in neighbouring Adamawa state.

The attacks have devastated Nigeria's northeast, one of the country's poorest regions where illiteracy and unemployment are rampant.

Seeking purpose and money, disillusioned and jobless young men have turned to the radical Islam of Boko Haram, which decries Western colonialism and the modern Nigerian state.

In their quest to carve out a caliphate, the militants have razed towns to the ground, kidnapped women and children and slaughtered thousands of others, putting many more on the brink of starvation.

Nigerian President Muhammadu Buhari came into power in 2015 vowing to stamp out Boko Haram, but the militants continue to stage frequent attacks, targeting both civilians and security forces.

The militants stormed the Government Girls Technical College in Dapchi on February 19, seizing over 100 schoolgirls in a carbon copy of the abduction in Chibok in 2014 that caused global outrage.

The deadly violence has put Buhari under pressure as elections approach in February next year.

Along with Boko Haram, Buhari faces the continued threat of militants in the oil-rich south, separatists in the southeast and an upsurge in communal violence in the country's central region.