Boko Haram militants attacked troops from Niger on an island base in Lake Chad, the government said Saturday, in a raid believed to have taken a heavy toll on the army.

"At dawn on April 25, fighters from the terrorist group Boko Haram riding motorized canoes attacked the island of Karamga, a position northwest of of the town of Bosso held by our defense and security forces," the ministry of defense said.

Suspected Boko Haram insurgents have forced hundreds of soldiers to flee Marte, a border town along the shores of the Lake Chad, a local official and witnesses said Friday. 

"The terrorists, numbering over 2,000, appeared from various directions on Thursday and engaged the soldiers in Kirenowa town and adjoining communities in Marte," said Imamu Habeeb, a local community leader.

Two drivers were shot dead in an attack on a peacekeeping supply convoy in northern Mali, authorities said Saturday, the second deadly assault on the United Nations in three days.

The assailants stopped the convoy some 15 kilometres (nine miles) from the main city of Gao and "coldly killed two of the drivers" in the attack Friday, the U.N. Mission in Mali, known as MINUSMA, said in a statement.

Seven civilians were killed in an attack in Chad blamed on Nigerian Boko Haram rebels, officials said Monday.

The Islamist militants ambushed people on their way to a market in Tchoukou Telia near Lake Chad on Friday, Dimouya Souapebe, the deputy prefect of Baga Sola told Agence France Presse.

Central and west African leaders will hold a summit next week to fine tune their campaign to crush Boko Haram, who appear to be losing ground in the face of a regional military offensive.

The April 8 talks will be the first since Nigeria's election a week ago which was won by Muhammadu Buhari, a former military leader who has vowed to rid his country of the "terror" the Islamist militants have sown.

The black letters crudely painted on a wall at the entrance to the devastated town of Malam Fatori, in northeast Nigeria, spell out "God is great" -- a calling card from the evicted Boko Haram fighters.

Niger and Chadian army troops, working together in support of Nigerian forces, recaptured the town on Tuesday to find grocery stores vandalised, smoke-blackened walls and motorbikes and wheelbarrows lying abandoned on the ground.

At least four people were killed Saturday when suspected Boko Haram fighters raided a local market in a village near the northeast Nigerian city of Maiduguri, security sources said.

Scores of Boko Haram gunmen stormed Kayamla village, 20 kilometers (12.5 miles) from Maiduguri, capital of restive Borno state, and opened fire on a weekly market, killing four traders, a senior security official in Maiduguri told Agence France Presse.

Troops from Niger and Chad killed 47 Boko Haram fighters when they repelled an attack by the Islamist insurgents in southeastern Niger, Chad's army said on Tuesday. 

The fighting took place in Bosso, a Niger village near the border with Nigeria.

The United Nations Human Rights Council will hold a special session next week on abuses by Boko Haram militants in Nigeria and neighboring countries, the council president said Friday.

The rights council rarely convenes special sessions, with only 22 held since the body was created in 2006.

More than 1,000 civilians have been killed in Boko Haram attacks in the first three months of this year, Human Rights Watch said on Thursday.

"Each week that passes we learn of more brutal Boko Haram abuses against civilians," the group's Nigeria researcher, Mausi Segun, said in an emailed statement.