Amnesty International on Wednesday called on Nigerian authorities to investigate unexplained disappearances, as the rights group highlighted a pro-Iranian Shiite religious movement that claims 600 of its members are missing. 

A botched air strike by the Nigerian Air Force earlier this week on a camp for people displaced by the Boko Haram insurgency killed at least 90 people, the Doctors Without Borders (MSF) aid group said Friday.

At least 30 people were killed on Friday when two female suicide bombers detonated their explosives in a busy market in northeast Nigeria, the military said. 

Boko Haram's elusive leader Abubakar Shekau broke his silence Thursday to insist he was "still around" following reports Islamic State had replaced him, but his message fueled talk of a split within the jihadist group.

For months, speculation has been rife over the fate of Shekau, who has led the Nigeria-based Islamist group since 2009 but has not been heard from since March.

Two would-be suicide bombers were killed in Maiduguri, northeast Nigeria, on Monday, after apparently trying to target an overnight Ramadan vigil, a civilian vigilante and a local resident said.

The Niger Delta Avengers (NDA) militant group on Wednesday rejected a truce offer to end attacks on key oil infrastructure that has cut output in Nigeria, and claimed another strike.

The NDA wrote on its Twitter account @NDAvengers: "We're not negotiating with any committee. If (the) federal government is discussing with any group they're doing that on their own."

Nigeria is planning peace talks with militants in the oil-producing south to end attacks that have slashed output, junior oil minister Emmanuel Ibe Kachikwu has said.

The military has deployed gunboats and fighter jets to the creeks of the Niger delta to hunt down the Niger Delta Avengers (NDA), blamed for a string of attacks since February.

A new rebel group on Monday vowed to attack strategic targets across Nigeria, despite calls for a united front but no "life-threatening actions" from other militants who have claimed recent strikes on oil facilities.

The group, calling itself the Joint Niger Delta Liberation Force (JNDLF), said it would hit "all those infrastructures that were built with our oil and gas monies in this country".

The Niger Delta Avengers said on Wednesday it had bombed two oil wells operated by U.S. energy group Chevron in Nigeria's oil-rich south, in the latest militant strike against production.

"With the heavy presence of 100 gunboats, four warships and jet bombers NDA blew up Chevron oil well RMP 23 and RMP 24 3:44 am (0244 GMT) this morning (Wednesday)," it said on Twitter.

Militants have attacked Nigerian state oil and gas pipelines in the Niger delta, the second sabotage in two days following an assault on Chevron infrastructure, a state official said Friday.

The attack on a Nigerian National Petroleum Corporation (NNPC) pipeline took place late Thursday near Warri, a city in Nigeria's increasingly volatile oil-producing south.