At least eight people have been killed in multiple suicide blasts along a highway in Maiduguri in northeastern Nigeria, officials said.
Two of those killed on Wednesday were civilians in a camp for displaced people on the outskirts of the city.
Police said five adult, male suicide bombers detonated explosives.
At the vast Muna camp, blasts triggered fires which burned down tents, Tijjani Lumani, a coordinator at the camp, told the AFP news agency.
"There were four explosions inside the camp. The bombers struck at different locations around 4:30am." Lumani said.
The camp houses tens of thousands of people who have fled violence in Nigeria's north, where the government is fighting the armed group Boko Haram.
There was no immediate claim of responsibility for the attacks but Maiduguri has been frequently targeted by Boko Haram fighters.
According to eyewitnesses, the bombers had sneaked into the camps late on Tuesday night alongside those who sell charcoal to refugees, who use it to cook their food.
There have been several attempted suicide bomb attacks near the Muna camp, Lumani said.
"We are vulnerable to Boko Haram. They can strike in the camp at any time," he said.
"All the suicide bombers who attacked the Muna garage just across the road from the camp and surrounding areas came in through the city gate only hundreds of metres from the camp."
Wednesday's blasts were the latest blamed on suicide bombers, who continue to pose a threat to civilians despite military claims of success against Boko Haram.
Four people were killed on Saturday when suicide bombers blew themselves up in a village near Maiduguri.
On Tuesday, Nigerian President Muhammadu Buhari met security chiefs in the capital Abuja to review the security situation in the country. The nearly seven-year Boko Haram crisis topped the agenda of the review, according to a presidential aide.
Maiduguri, the state capital of Borno state, is the birthplace of the Boko Haram insurgency, which has claimed the lives of over 20,000 people and forced 2.6 million from their homes since 2009.
Source: Al Jazeera and news agencies