ABUJA (Reuters) - Suspected Boko Haram militants killed at least 11 people including three aid workers in an attack on a military barracks in Nigeria’s northeastern Borno state late on Thursday, according to two security reports seen by Reuters.

UNHAS members assist with the relocation of aid workers after an attack in the town of Rann, at Maiduguri Airport, Nigeria March 2, 2018. OCHA/Yasmina Guerda Handout via REUTERS

The raid in the town of Rann marks the latest high-profile assault by the jihadists in the northeast, coming less than two weeks after militants abducted 110 girls from a school in the town of Dapchi in neighboring Yobe state.

The United Nations confirmed three aid workers, all Nigerian nationals, were killed in the attack in Rann, near the Cameroon border, and said a female nurse was missing, feared abducted. It was concerned other civilians may have been killed or injured.

The whereabouts of two midwives are also unknown, according to an International Committee of the Red Cross spokeswoman, who said no Red Cross staff were injured or missing.

Four soldiers and four police officers were killed, according to the Nigerian security reports.

The militants, armed with rocket-propelled grenades and truck-mounted guns, initially overpowered soldiers in a firefight at the military barracks, but the armed forces later regained control, according to the two reports.

The attack was a further setback for President Muhammadu Buhari, who took office in May 2015 vowing to improve security and who has repeatedly asserted that the Boko Haram insurgency has been defeated.

Buhari said the attack showed Boko Haram was “godless, brutish, and utterly to be despised”.

“No true religion advocates hurting the innocent. To now further attack and kill those offering humanitarian aid is the height of bestiality,” he said in an emailed statement.

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SEARCH FOR ABDUCTED GIRLS

His statement was issued hours after the government said it was extending to neighboring countries the search for the girls taken in Dapchi, which is some 400 km (250 miles) west of Rann.

Borno state, where Rann is situated, is the epicenter of the nine-year-old insurgency, which aims to impose a strict interpretation of Islam in the northeast of Africa’s most populous country. More than 20,000 people have been killed and some two million forced to leave their homes since 2009.

Two of the aid workers who died were contractors with the International Organization for Migration (IOM), working as coordinators at a camp for 55,000 displaced people in Rann, the United Nations said.

The third was a doctor employed as a consultant for UNICEF.

“We call on authorities to ensure the perpetrators are brought to justice and account,” Edward Kallon, the U.N. Humanitarian Coordinator in Nigeria, said in a statement.

IOM official Mohammed Abdiker said staff were “outraged and saddened” by the death of their colleagues.

Medical charity Medecins Sans Frontieres said it had suspended its work in Rann following the attack and evacuated both national and international staff.

Attacks on aid workers are rare, but not unheard of, in Nigeria. In December, four people were killed when a World Food Programme (WFP) convoy was ambushed in Borno state.

Boko Haram held a swathe of territory in northeast Nigeria around the size of Belgium in late 2014. It was pushed out of most of that land by Nigeria’s army, backed by troops from neighboring countries, in early 2015.

Although it has failed to control large areas of land since then, the group continues to carry out suicide bombings and gun raids in northeast Nigeria, Cameroon, Niger and Chad.

The camp for displaced people in Rann was bombed in a Nigerian Air Force strike last year, killing up to 170 people.