Kano - Boko Haram still poses a threat to civilians, despite a military crackdown, officials and experts said on Tuesday, after hundreds of bodies were found in Borno State.
The grim discovery in Damasak, near Lake Chad in the far north of Borno state, came as the local government looked at the feasibility of returning thousands of people who fled the violence.
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Decomposing bodies were found in houses, on the streets and in a dried up river, some of them covered in desert sand, although it was unclear when the killings took place.
The deaths, the level of destruction in the town, which was retaken in early March, and a separate attack that killed 21 displaced people in Yobe state, underlined the continuing risks posed by the Islamists.
The chairman of the Borno State Emergency Management Agency (SEMA), Grema Terab, said more than 100,000 people were living in camps in the state capital Maiduguri or with relatives.
"But we would not allow them to back to their domains until we (have) fully secured the towns and villages," he added.
Bulama Mali Gubio, from the Borno Elders Forum civil society group, also called for tighter security before the displaced can return, including a permanent presence of troops.
"There is no way people can go back to their homes in the present arrangement where soldiers leave the areas they retake from Boko Haram the moment the insurgents are pushed out," he told AFP.
"Every time soldiers retake a town from Boko Haram the insurgents flee into the bush and lurk around. Once they understand the troops have withdrawn they resurface," he added.
Gubio said there needed to be greater cooperation between the state and federal authorities, as well as the international community and private sector, to secure and rebuild the areas.
"If we work in cooperation like a colony of ants we shall make substantial progress in six months," he added, pointing to post-conflict rebuilding in places such as Vietnam and Bosnia.
At least 15,000 people have been killed since 2009 and more than 1.5 million made homeless as a result of Boko Haram's fight to create a hardline Islamic state in northeast Nigeria.
On Friday, 21 internally displaced people (IDPs) were killed after returning to their homes in Bultaram village, in the Gujba area of Yobe, to collect abandoned food supplies.
A separate attack on Saturday targeted Nigerien soldiers stationed on an island on Lake Chad before the militants turned their guns on civilians.
Earlier this week, Islamist fighters forced hundreds of troops from Marte, also near Lake Chad, although the military denied the claim and said it had instead made a tactical withdrawal.
Security analysts said the attacks showed that despite an apparent lull and coalition forces claiming success against Boko Haram, the Islamic State-allied group was still present and a threat.
"If Boko Haram could retake Marte with all the security deployment there it goes to show other areas with less security protection can be retaken," said Bawa Abdullahi Wase, who tracks the conflict.
Some suggested they were biding their time, possibly regrouping and adapting strategy to the operations by coalition troops, as well as its new affiliation with the IS group.
"Odds are it will only get worse," said Yan St-Pierre, from the Modern Security Consulting Group (MOSECON) in Berlin, recalling the wave of attacks that followed a similar hiatus last September.
Boko Haram could now be conducting "business as usual", which could test the ability of the coalition to work together successfully," he added.
Ryan Cummings, chief Africa analyst at consultants Red24, suggested Boko Haram may have tactically retreated, particularly to northern Cameroon, to avoid confrontation with the coalition.
Focus now for incoming president Muhammadu Buhari and the country's neighbours is tackling Boko Haram within and outside its traditional area of operation, he added.
"Given the prevailing situation, I think one would be hard-pressed to support the re-population of IDP's in the northeast," he told AFP in an email exchange.
"The fact is that the conditions which made them vulnerable to violence in the first place, is the presence of a predatory armed group and a lack of governance/security structures, remains relevant in the current context," he said.
Military victories against Boko Haram would likely spur the group to carry out retributive attacks against "soft" targets, with civilians in the firing line, he added.