The Islamist extremist group Boko Haram carried out attacks on the settlements, a government official said on Thursday. At least a hundred people were killed when the militants took over the town of Baga by Lake Chad, regional politician Abba Hassan said.
Hassan's estimate of at least 100 dead differed wildly from earlier, unconfirmed reports claiming as many as 2,000 casualties in and around Baga. A government official, speaking to news agency Reuters on condition of anonymity, rejected these reports.
Two locals said the insurgents began shooting indiscriminately and burning buildings in raids on the civilian population carried out on Wednesday. News of the attacks was delayed because of poor telephone communications.
"I escaped with my family in the car after seeing how Boko Haram was killing people. I saw bodies in the street. Children and women, some were crying for help," Mohamed Bukar told Reuters after fleeing to the Borno state capital Maiduguri.
Boko Haram was reported to have attacked Baga several days previously, taking over a military base. News that the insurgents had returned to the town and surrounding settlements in the Lake Chad region came as Nigerian President Goodluck Jonathan launched his bid for a second term at a mass rally in Lagos. Jonathan took time to condemn the shootings in Paris at the offices of satirical newspaper Charlie Hebdo, but made no reference to the Boko Haram attacks. His government has been criticised for its lack of effective response to the Islamic group's attacks.
At the same time, Chad's Prime Minister Kalzeubet Pahimi has appealed for international aid for thousands of Nigerian refugees who have fled. At least 2,000 Nigerians and 500 Chadians crossed the border into Chad in recent days, joining around 1,000 Nigerians who arrived some months ago.
Earlier on Thursday, Cameroonian President Paul Biya called for international help to stop Boko Haram, a day after the Islamist terrorist group threatened to escalate attacks in Cameroon.
"From Mali to Somalia and the Central African Republic, these terrorists have the same agenda," Biya said. "A global threat requires a global response."
The Boko Haram militants have been waging an insurgency to establish an Islamic state in Nigeria's northeast for five years. The number and scale of attacks rose sharply last year, after the government imposed emergency rule on the three worst-hit states.