Multiple blasts at camps for people who have fled the Islamist militants Boko Haram killed four and injured 18 in the northeastern Nigeria city of Maiduguri, the state police commissioner said on Wednesday.
The attacks were the latest in a series in the past week. In a video circulated on Friday, a man claiming to be Boko Haram's leader claimed responsibility for bombings in Maiduguri and a raid in a nearby town last week. Bombings near the city killed four on Sunday.
Borno Police Commissioner Damian Chukwu said the latest blasts happened around 4:30 a.m. (0330 UTC).
"Three bomb explosions occurred this morning at three different locations near Muna Garage, Maiduguri. Four people were killed and 18 people injured," he said.
Chukwu said two of the blasts happened at camps for people displaced by Boko Haram. The frequency of attacks has increased since the end of the rainy season in late 2016.
Maiduguri has been the city worst hit by Boko Haram's eight-year-old campaign to create an Islamic caliphate in northeastern Nigeria.
Boko Haram violence has displaced more than 2 million people and killed at least 20,000, according the United Nations.
Since Boko Haram first took up arms against the Nigerian government in 2009, trade routes and farming activity have been disrupted.
Although Nigerian President Muhammadu Buhari has led a successful military campaign against the militant group since he assumed office, Boko Haram is still capable of executing deadly attacks.
The violence is not limited to northeastern Nigeria and has spilled over into Niger, Chad and Cameroon.