Boko Haram militants killed at least 60 people in an attack on the northeast Nigerian town of Rann on Monday, Amnesty International said on Friday, February 1.

One of the deadliest incidents in the insurgency that began in 2009, the attack came two weeks after fighters from the Boko Haram faction led by Abubakar Shekau overran the same town and its camp for internally displaced people, diving out the military, and burning homes and other structures.

#Rann: Amnesty International also analyzed satellite imagery which shows hundreds of burned structures in the town. Many of the destroyed structures only date back to 2017, suggesting they were shelters for internally displaced people who came to Rann seeking protection. pic.twitter.com/bl7rh19li2 — Amnesty Int. Nigeria (@AmnestyNigeria) February 1, 2019

Around 175 km (110 miles) northeast of Borno state capital Maiduguri near the border with Cameroon, Rann hosts some 35,000 internally displaced people, according to the International Organization for Migration.

“At around 9am on 28 January, a group of Boko Haram fighters arrived on motorcycles. They set houses ablaze and killed those left behind. They also chased after those who attempted to escape and killed some people outside the town,” Amnesty said in a release.

One eyewitness, a member of the Civilian Joint Task Force militia that works alongside the Nigerian military, told Amnesty that 11 bodies were found in the town and 49 outside.

“Ten of us came from Cameroon to Rann for the burial. When we arrived, we found and buried 11 corpses within the town, but the soldiers told us that they buried several others yesterday [January 30] who had decayed,” the witness said. “Outside the town, we recovered and buried 49 dead bodies all with gunshot wounds.”

“We have now confirmed that this week’s attack on Rann was the deadliest yet by Boko Haram, killing at least 60 people,” Osai Ojigho, Director of Amnesty International Nigeria said in the release.

Amnesty said it was told that about 50 people have not been accounted for.

The Norwegian Refugee Council on January 30 said 30,000 people fled to Cameroon from Rann.

#Rann: Aid agencies have reported that some 30,000 civilians have fled for the border with Cameroon in recent days, joining a further 9,000 who fled #BokoHaram’s previous attack on Rann on 14 January. #Nigeria. Satellite image of #Rann after the attack: pic.twitter.com/0w91Me9BcF — Amnesty Int. Nigeria (@AmnestyNigeria) February 1, 2019

Amnesty also analyzed satellite imagery from January 30 which shows hundreds of burned structures in Rann, and suggested many were shelters for IDPs. It said environmental sensors detected fires in the area on January 28 and 29, and that the two recent attacks have left most of the town damaged or destroyed.

The Nigerian town of Rann was overrun by Boko Haram (unsure if ISWA) in mid-Jan. Since Jan 27th over 35,000 indivduals have fled from the town across the border to Cameroon. These images from @PlanetLabs shows the extend of burning inside the town and an overlay of burnt areas. pic.twitter.com/eyFOYBpehm — Nathan Ruser (@Nrg8000) February 1, 2019

Calls for investigation into troop withdrawal

Amnesty called for an investigation into the alleged withdrawal of security forces from Rann.

The troops allegedly left after the January 14 attack when fighters from Abubakar Shekau’s faction of Boko Haram overran the military base and IDP camp.

After Cameroonian Multi-National Joint Task Force troops had retreated across the border, Nigerian soldiers left the town because they had insufficient troops, weapons and equipment, a security source told Reuters.

AFP was told Nigerian soldiers withdrew because there were not enough of them to repel a strong Boko Haram attack.

There were reports that the Nigerian Army returned to Rann on January 29. The security source told Reuters that Nigerian troops had returned, along with Cameroonian MNJTF troops.

Two security sources told AFP that a senior military officer had gone to Rann on January 30 to supervise the deployment of troops and weapons after the Boko Haram attacks. His convoy was attacked by Islamic State West Africa province fighters while travelling back to Dikwa from Rann.

Medecins Sans Frontieres (Doctors Without Borders) said that 14 people including three soldiers were killed in the January 14 assault and by January 16 around 10,000 displaced people were forced to flee the area, heading to Cameroon. Those refugees were subsequently forced to return, NRC said.

Shekau’s Boko Haram faction later claimed the January 14 Rann attack in a video.

Rann has now been hit four times since March 2018.

In an attack on March 1, eight security personnel and three aid workers were killed. Three other aid workers were kidnapped, two of whom were later executed.

On December 6, Boko Haram fighters attacked a military base in Rann, but it was unclear which faction they belonged to. After an hour’s heavy fighting, the militants were pushed out with aerial support, one security source told AFP.

More than 27,000 people have been killed since the Boko Haram jihadist insurgency began in 2009, and 1.8 million people are still homeless and in need of humanitarian assistance.

Boko Haram split into two factions in mid-2016. One is led by Abu Mus’ab Al-Barnawi and largely focuses on attacking military and government targets, while the other, led by Abubakar Shekau, is notorious for suicide bombings and indiscriminate killings of civilians.

Shekau pledged allegiance to ISIS leader Abu Bakr Al-Baghdadi, but ISIS central only gives formal backing to the Barnawi faction, which is known as Islamic State West Africa province.

Both factions of Boko Haram have intensified attacks in the region over several months, but the upsurge in ISWA attacks has been much more serious. Amid signs of a takeover by more hardline leaders, the group has launched dozens of assaults on military targets in Borno and Yobe states.

ISWA attacks have increasingly featured in ISIS propaganda, with a number of assaults on the Nigerian military claimed over the past week.

The attacks come as Nigeria gears up for crucial elections with security becoming a major campaign issue.

Nigeria’s President Muhammadu Buhari was elected in 2015 on a promise to end the conflict and he is seeking a second term in the presidential election on February 16. National Assembly elections will be held the same day, while regional polls are set for March 2.

Buhari said in December 2015 that Boko Haram was “technically defeated” after a sustained counter-insurgency. But on January 9 he acknowledged setbacks in the fight-back, including “battle fatigue” among soldiers from a wave of guerrilla style hit-and-run tactics and suicide bombings.