At least 74 people were killed in attacks blamed on Boko Haram militants this weekend, taking the overall death toll this year beyond 300, with no apparent end in sight to the carnage, AFP reports.
Nearly 250 people had lost their lives since the turn of the year, even before the latest attacks, which saw twin blasts rip through the capital of Borno state, Maiduguri and heavily armed gunmen then open fire on a nearby village.
The attacks will likely renew fears that Nigeria is struggling to contain the Islamist insurgency and the perception that militant fighters are able to roam the northeast with impunity, attacking at will.
At least 35 people were killed in the crowded Gomari district of Maiduguri, many of them food vendors and children hawking goods, as locals prepared for evening prayers on Saturday.
"We are still counting. So far we have counted 35 bodies. Our men are still working with rescue workers at the scene," Borno state police commissioner Lawal Tanko told AFP.
Witnesses said the final death toll could rise and as many as 50 people may have been killed and dozens of homes razed in the blasts.
Less than an hour later, gunmen dressed in military fatigues and armed with powerful assault rifles, rocket-propelled grenades and explosives laid siege to the village of Mainok 50 kilometres (30 miles) away, killing 39.
Separately, there were claims that 20 people were mistakenly killed in the village of Daglun, also in Borno state, during bombardment by airforce jets of suspected militants but the military denied the claim.
There was no immediate comment from Nigeria's government, which has maintained that it is successfully tackling the violence, but French President Francois Hollande condemned the attacks "with the greatest possible rigour".
Hollande visited Abuja last week and told his counterpart Goodluck Jonathan that Nigeria had France's full support.
Borno and two other northeastern states, Yobe and Adamawa, have been under emergency rule since May last year and an increased military presence had pushed Boko Haram out of towns and cities into more remote, rural areas.
But Saturday's blast in Maiduguri came after at least 43 people, most of them students, were killed as they slept when suspected Boko Haram gunmen burst into their secondary school dormitory.
At least 32 were killed in co-ordinated attacks in three separate locations on Wednesday in Adamawa state, including at a Christian theological college.
Borno state governor Kashim Shettima last month claimed that Nigeria's military was outgunned by Boko Haram after an attack on a mostly Christian village on February 15 left 106 people dead.
The International Crisis Group said in its monthly "CrisisWatch" bulletin on conflicts around the world that the Boko Haram insurgency had deteriorated in February.
The attacks have also attracted concern from foreign governments to the United Nations, in particular because the majority of victims were civilians and schoolchildren.
There are increasing worries of a humanitarian crisis, as people in the three states flee their homes in fear.
The UN said last Thursday that a total of 290,002 people had been internally displaced in Adamawa, Borno and Yobe between the start of emergency rule and January 1 this year.
Military claims successes
Nigeria's military said on Sunday evening that it had killed a number of Boko Haram fighters, including those thought responsible for last week's school attack in Yobe.
Defence ministry spokesman Chris Olukolade said an unspecified number of people had been arrested on suspicion of detonating Saturday's bombs in Maiduguri.
But he said claims that civilians were killed in air operations against Boko Haram in Borno were untrue.
"The reports are believed to be part of the design by those bent on discrediting the counter-terrorist mission," he added.
On Friday, the military claimed to have killed 13 suspected Islamists and arrested 15 others after a raid on a camp between Borno and Adamawa the previous day.
Boko Haram, which in the local Hausa language of the Muslim-majority north means "Western education is sin", claims to be fighting to create a strict Islamic state in the mainly Muslim north.
The sect has since 2009 carried out attacks across the north and centre of the country but the violence has in recent months been concentrated in the northeast, the region where Boko Haram was founded more than a decade ago.