Nigeria's military on Monday claimed the recapture of Monguno, a garrison town in northeast Borno state, after it was seized by Boko Haram Islamist militants last month.

The insurgents suffered casualties and the military operation disrupted an attempt to re-supply fighters in the flashpoint town of Baga with weapons and food, a statement said.

Central African leaders began talks Monday in Cameroon's capital Yaounde on a joint strategy to tackle the extremist Boko Haram group, officials said.

Six heads of state attended the meeting held under the aegis of the Economic Community of Central African States (ECCAS), while four other countries sent delegates.

Thirteen people have now died as a result of a female suicide bomb attack at a bus station in the northeast Nigerian city of Damaturu, police said on Monday.

"The death toll from the suicide attack at the Damaturu motor park now stands at 13, with the death of six more victims at the hospital," Yobe state police spokesman Toyin Gbadegesin told Agence France Presse.

Several dozen people suspected of having links to Nigeria's Boko Haram have been arrested in southern Niger since the start of cross-border attacks by the Islamist group a week ago, a local governor said.

"In the region of Zinder, we have a few dozen people whom we arrested for checking. They are suspects," Kalla Moutari told AFP in an interview late Saturday, adding that they were citizens of Niger.

Nigerian President Goodluck Jonathan is appealing to the United States for greater military assistance in the fight against Boko Haram Islamists, according to the Wall Street Journal.

"Are they not fighting ISIS? Why can't they come to Nigeria?" Jonathan told the newspaper in an interview published Friday, referring to the Islamic State group. 

Boko Haram invaded the restive northeastern Nigerian city of Gombe on Saturday and warned residents against voting in next month's elections as the Islamists defied regional force aiming to pursue them.

Residents said the attackers later left the city and stormed another area some 40 kilometers (25 miles) away, where they burned homes.

Nigerian President Goodluck Jonathan on Friday on Friday promised there would be no further  vote delays, after the electoral agency pushed back the presidential and parliamentary polls by six weeks to May.

"We will surely conduct elections as scheduled. We promise you. Communicate this to your homes that elections will be conducted as scheduled and on 29th of May, there will be an inauguration of a president of this country," he told the foreign envoys.

Political violence in the run-up to Nigeria's election has killed 58 people, with rising "hate speech" between rival camps threatening to spark further unrest, the country's human rights commission (NHRC) said Friday.

"If urgent steps are not taken to arrest further escalation, Nigeria's 2015 general elections would confront a high risk of significant violence," the commission said in a new report.

Nigeria-based Boko Haram Islamists carried out their first attack Friday inside Chad, killing five people in a strike on a village on the shores of Lake Chad, a security source said.

Chadian military spokesman Azem Bermandoa Agouna also confirmed the pre-dawn attack on Ngouboua, a village across the water from the Nigerian town of Baga.

Chad's President Idriss Deby has taken up the fight against Boko Haram at the risk of offending diplomatic sensibilities in Africa, but to the delight of his international allies.

One Western diplomat described Deby, who seized power in 1990, as "first and foremost a fighter," who for years had battled rebels intent on ousting him from power, while at the same time arming those fighting the authorities in neighboring Sudan.