Ibrahim fled his home in Gwoza, northeast Nigeria, in August last year, when invading Boko Haram fighters took over the town as part of the Islamist group's self-declared caliphate.

The businessman lost his home, cars, money and his brother, who was shot dead as they fled the carnage, spending 14 days on the road and barely eating.

Nigerian troops have rescued 338 people, mainly women and children, held by Boko Haram Islamists around the group's Sambisa forest stronghold in the restive northeast, the army said Wednesday.

"The (army) unit ... rescued 338 persons that were held captive by the terrorists," the army said of an operation on Tuesday, adding that 192 of the survivors were children and 138 women.

Two bomb blasts ripped through mosques in northeast Nigeria on Friday, killing at least 55 people and injuring more than 100, as Boko Haram fighters seized a town in neighboring Cameroon.

The attacks in Maiduguri, Yola and Kerawa again underlined the persistent national and regional threat from the Islamist militants, despite military claims of gains.

At least 34 people were killed in a wave of suicide bomb attacks in northeast Nigeria, as the military on Friday warned Boko Haram militants threaten the country's sovereignty.

Thirty died in a double bombing on a mosque in Molai on Thursday night, Mohammed Kanar, from the National Emergency Management Agency (NEMA) said.

Four people were killed when three suicide bombers blew themselves up in a suburb of the northeastern Nigerian city of Maiduguri, the army said on Wednesday.

"The explosions occurred at three-minute intervals and seven people were confirmed dead, including the three suicide terrorists," said army spokesman Colonel Sani Usman.

Nigeria has warned civilians that Boko Haram is using deadly cluster bombs but campaigners say the Islamists may have got the banned weapons from the military in the first place.

Defense spokesman Rabe Abubakar urged people to be on their guard for "cluster bombs, sometimes called scatter bombs", as engineers had recently found caches in northeastern Adamawa state.

At least 14 people were killed in three separate suicide bomb attacks in northeast Nigeria on Wednesday, with suspicion falling on radical Islamist group Boko Haram after a string of similar strikes in recent months.

The triple blasts in the Yobe state capital, Damaturu, came after the militants this week claimed to have carried out three suicide attacks near Abuja last Friday that left 18 dead.

Boko Haram Islamists attacked Chadian soldiers on Tuesday, killing 11 and wounding 13, a Chadian security source said, in the latest deadly raid by the militants despite a regional offensive against them.

The source said 17 Boko Haram fighters also died in the fighting following the pre-dawn strike near the Nigerian border and Lake Chad.

Boko Haram has claimed responsibility for twin bomb attacks on the outskirts of Nigeria's capital, Abuja, the group said in a message posted on social media on Sunday evening.

At least 18 people were killed and 41 injured in the bombings on Friday night, in Kuje, to the west of Abuja, and in Nyanya, to the east, the authorities said.

An alleged Boko Haram attack on a village in southeastern Niger killed two of the country's soldiers, the Nigerien army said Friday, the latest deadly raid by the Islamist group.

The incident occurred when a nearby military unit was warned that an attack was imminent against the village of Baroua, near the border with Nigeria, at around 10:30pm (2130 GMT) on Thursday, and dispatched soldiers to the scene, according to a defense ministry statement read on state television.