Suspected members of Boko Haram have seized a military base in northeastern Nigeria in a series of blistering raids near Lake Chad, sending soldiers and civilians fleeing, witnesses said on Sunday.
Local residents reported that the gunmen killed several people, burnt hundreds of homes and looted scores of businesses in Saturday's attacks, although there was no official death toll.
The fighters are believed to control large swathes of land in northeastern Nigeria since launching an uprising in 2009 that has now claimed more than 13,000 lives.
The insurgency has killed more than 10,000 people this year, according to a count by the Council on Foreign Relations in November. It is a grave threat to Nigeria, Africa's biggest economy, and a serious challenge to President Goodluck Jonathan, who faces an election challenge on Feb. 14 from opposition leader Muhammadu Buhari, a former military ruler seen as tough on security.
After beginning their fight for an Islamic state five years ago in the northeastern city of Maiduguri, Boko Haram has radiated outwards into porous border areas, threatening Nigeria's neighbors around the Lake Chad Basin.
Baga, the site of the attack, is notionally the headquarters of a multinational force comprising troops from Niger, Nigeria, Chad and Cameroon, although only Nigerian troops are actually stationed there.
Troops eventually fled the remote station on the semi-desert shores of Lake Chad after it was attacked on Saturday by Boko Haram fighters in military vehicles, two security sources told Reuters. The military did not immediately respond to a request for comment.
"They overwhelmed the troops and forced them to abandon the base which the gunmen took over," local resident Usman Dansubdu told AFP after fleeing to neighbouring Chad.
Hundreds of fear-stricken residents from Baga and five other Nigerian towns and fishing villages poured into Chad to escape the raids on their homes, witnesses said.
Maina Ma'aji Lawan, the senator representing northern Borno where Baga is located, confirmed the attack on the military base and other five locations. "Boko Haram insurgents launched attacks in Baga area yesterday (Saturday), destroying six towns and several settlements, forcing the people in the affected places to flee into Chad," he told AFP. "They came in unbelievably large numbers and overpowered the multinational troops and local vigilantes. They took over the multinational troop base in Baga and sent the soldiers fleeing."
Residents of Kauyen Kuros, Mile 3, Mile 4, Baga, Doron-Baga and Bundaram fled across the lake in fishing boats and canoes into Chad following the hours-long attacks by hundreds of fighters.
"We are now seeking refuge in Gubuwa, Kangallam and Kaiga villages inside Chad near the border with Nigeria," Dansubdu told AFP by telephone from Gubuwa.
The gunmen killed several people, burnt hundreds of homes and looted scores of businesses in the attacks that lasted over seven hours, said Doron-Baga resident Lawan Ajikalumbu who also fled to Gubuwa.
There was no official casualty toll.
Abubakar Gamandi, head of the fishermen's union in Borno state and a resident of Baga, said he received several calls from union members who fled to neighbouring Chad informing him of the attacks.
Baga was the scene of the deadliest Boko Haram attack in April 2013 when 185 people were killed and more than 2,000 homes were destroyed in fighting between the Islamists and members of the multinational force.
Suspected Boko Haram gunmen late Saturday also raided the town of Babban Gida, 50 kilometres (30 miles) from Damaturu, the capital of neighbouring Yobe state, according to residents.
The militants destroyed the military barracks, torched a deserted government boarding school and a local administration building after overpowering soldiers in a gunfight, they said.