The medical charity Medecins Sans Frontieres (MSF) said on Friday it had suspended its work in the Nigerian town of Rann and evacuated national and international staff after a deadly raid by Boko Haram guerrillas.

Suspected Boko Haram gunmen killed four Nigerian aid workers in an attack on a military barracks in the town in Borno state late on Thursday.

“Following a violent attack in Rann, Borno state, on Thursday 1 March, Médecins Sans Frontières (MSF) suspended its medical activities in the town and evacuated 22 national and international staff,” MSF said in a statement.

“It is still unclear how many people were killed and injured but before leaving, MSF medical staff treated 9 wounded patients.

“This attack is a stark reminder that it is the people in Borno who are paying the price of this ruthless conflict”, MSF said.

“Leaving our patients without medical assistance is an extremely painful decision”, it added.