Doubts persisted on Tuesday over a Nigerian military claim that the leader of Islamist extremist group Boko Haram may have been killed, with questions raised over the timing of the announcement.
A security task force in northeastern Nigeria issued a statement on Monday saying Abubakar Shekau, declared a "global terrorist" by the United States, "may have died" from a gunshot wound after a clash with soldiers on June 30.
"It is greatly believed that Shekau might have died between 25 July to 3 August 2013" after being taken over the border into Amitchide in neighbouring Cameroon, the statement said.
It was issued on the day the task force wrapped up its work and handed over duties to a newly created military division charged with the battle to end Boko Haram's four-year insurgency.
Task force spokesman Lieutenant Colonel Sagir Musa declined to comment when contacted on Tuesday, saying he had left Maiduguri, the epicentre of Boko Haram's insurgency and where the force was based.
National defence spokesman Brigadier General Chris Olukolade distanced himself from the statement when contacted by AFP, while local media reported on Tuesday that there was unease within the military over the claim.
"We are yet to get confirmation on that," Olukolade told AFP on Monday. "We are talking to our troops in the field."
He could not be reached on Tuesday.
The widely-read Punch newspaper said senior members of the military were unhappy with the statement because there was not yet enough evidence to make such a claim.
It quoted a senior security source saying: "The hurried release of the news of the killing of Shekau on the date a new division of the Nigerian army was taking over from the JTF was rather suspicious," referring to the task force.
Other newspapers reported similar concerns, saying information has been circulating about claims of Shekau's death, but the intelligence was still being analysed.
Security analysts also urged caution.
"The military statement is not definite," Nnamdi Obasi, Nigeria researcher at the International Crisis Group, told AFP.
"It didn't provide any hard evidence. Even in the way they said it, they don't seem to be absolutely sure themselves."
Shekau has been considered the leader of the main Islamist extremist faction of Boko Haram and the United States in March put a $7 million (5.3 million euro) bounty on his head.
The US embassy has not commented and the US online wanted notice for Shekau had not been updated.
Boko Haram's insurgency has left at least 3,600 people dead since 2009, including killings by the security forces, who have been accused of major abuses.
Boko Haram's targets have included security forces, churches, worshippers at mosques and UN headquarters in Abuja, among others.
Nigeria's military began a sweeping offensive in the northeast in May aiming to end the insurgency.
Shekau has often sent out video messages from unknown locations. In a video message seen by AFP on August 12, a man who appeared to be Shekau insisted that he was in good health and referred to attacks in early August.
The military statement said the video was a fake.
Boko Haram has claimed to be fighting for the creation of an Islamic state in Africa's most populous nation and largest oil producer, though the group is believed to have a number of factions with varying aims.
Nigeria's 160 million population is roughly divided between a mainly Christian south and mostly Muslim north.
Western nations have closely monitored the group for signs of cooperation with outside extremist organisations.
Boko Haram members have sought training in northern Mali with Al-Qaeda's north African branch, known as Al-Qaeda in the Islamic Maghreb. There have also been suspicions over links with other groups in Somalia and Yemen, but the degree of contact is unclear.
The US wanted notice for Shekau says that "there are reported communications, training, and weapons links between Boko Haram, Al-Qaeda in the Lands of the Islamic Maghreb, Al-Shebab, and Al-Qaeda in the Arabian Peninsula, which may strengthen Boko Haram's capacity to conduct terrorist attacks."