By Lanre Ola and Abdoulaye Massalaki
BAUCHI, Nigeria/NIAMEY, Niger (Reuters) - Nigerian forces backed by air strikes seized the northeastern border town of Baga from Islamist group Boko Haram on Saturday, the military said, a significant victory in an offensive against an insurgency affecting four African states.
Retaking the town - at Nigeria's border with Chad, Niger and Cameroon - was one of several in the past two weeks, and particularly important as Baga was the headquarters of a multinational force of troops from all four countries.
The militants had claimed a Jan. 3 attack that killed scores, possibly hundreds, and left the jihadists in control.
"We have secured Baga. We are now in full control. There are only mopping up exercises left to do," Defence Spokesman Major-General Chris Olukolade said by telephone.
In a statement minutes earlier Olukolade had said that "a large number of terrorists had drowned in Lake Chad" as troops advanced on Baga.
The Islamist fighters appear to be on the run in many parts of Nigeria and regions near its borders, after being subjected to a major offensive on all sides, although they have seemed defeated in the past only to bounce back deadlier than ever.
"Not even the strategy of mining over 1,500 spots with land mines on the routes leading to the town could save the terrorists from the aggressive move of advancing troops," Olukolade had said in a statement earlier in the day.
Successes in pushing back Boko Haram are welcome news for Nigeria's President Goodluck Jonathan as he faces an election on March 28 that was delayed by six weeks on the grounds that more time was needed to fight the insurgency.
The poll, however, also provides a strong motive for the government and military to talk up successes.
LAKE CHAD FIGHTING
The Sunni Islamist militants have killed thousands of people and kidnapped hundreds in a six-year insurgency and have gained strength in the past year, carving out a territory the size of Belgium and intensifying cross-border raids.
To counter that threat, neighbouring states, where Boko Haram fighters habitually flee after hit-and-run attacks, are pursuing a strategy of pushing them back into Nigeria.
A spokesman for Chad's army said his troops did not participate in the Baga offensive. Niger and Cameroonian militaries were not immediately available for comment.
But in a sign of their ability to strike at neighbours, at least 23 people were killed in fighting overnight in an attack on the island of Karamga, on the Niger side of Lake Chad, held by Niger's army.
Niger's President Mahamadou Issoufou reiterated a pledge to defeat the group in a speech in the southern border town of Diffa, the scene of a wave of attacks this month.
"We are going to win this war because we are not alone," he said on Saturday outside an army barracks. "We will come out from this test more experienced and battle-hardened."
In a visit to Chad and Cameroon on Saturday, French defence minister Laurent Fabius expressed his solidarity and said international allies needed to give more financial support.
"We are working to get the force off the ground and contribute financially so that the burden is not heavy on the countries concerned," he said, referring to an 8,700-strong force from the four countries plus Benin that military chiefs plan to agree on next week in Chad's capital N'Djamena.
"We want a donor conference which could help with the financial charges," he said.
France already provides intelligence and logistical support to regional armies but has stopped short of direct intervention, despite a strong military presence across the region.