Suspected Islamist militants have launched a brazen daytime attack in the northeastern Nigerian city of Maiduguri.
Witnesses say gunmen armed with explosives stormed the Giwa military barracks Friday morning, setting off a fierce gun battle with soldiers. The attackers also set fire to homes in a residential area and opened fire on civilians.
Nigeria's defense ministry says "pockets of terrorists" attacked the barracks in an apparent attempt to free "colleagues" detained at the site.
In a statement, a defense official AC Olukolade said they attack was "successfully repelled," with the terrorist suffering heavy casualties. Four soldiers were wounded during the incident.
Nigerian media outlets report that at least some of the attackers came dressed in military uniforms.
There was no immediate claim of responsibility.
Maiduguri is the home city of the radical sect Boko Haram, which for more than four years has battled government to create a strict Islamist state in the country's predominantly Muslim north.
On Friday, Human Rights Watch said Boko Haram had launched attacks in over 40 villages in northeastern Nigeria since the start of 2014.
The rights group says the militants have carried out "almost daily killings, bombings, thefts" and other crimes that have led to the deaths of 700 people so far this year.
Efforts by the Nigerian military to stamp out the group have not stopped the violence.
Friday's suspected militant attack took place as U.N. High Commissioner for Human Rights Navi Pillay was visiting the Nigerian capital, Abuja.
Pillay said the alleged Boko Haram attacks had "grown increasingly monstrous."
However, Pillay also said many people had told her that Nigerian security forces had been committing human rights violations that were alienating communities and creating "fertile ground" for Boko Haram recruiting efforts.