FILE PHOTO: The leader of one of the Boko Haram group's factions, Abubakar Shekau speaks in front of guards in an unknown…
FILE - Boko Haram leader Abubakar Shekau speaks in front of guards at an unknown location in Nigeria in this still image taken from an undated video obtained Jan. 15, 2018.

WASHINGTON - The United States is not ready to declare the leader of Nigeria's Boko Haram terror group dead, despite reports from the region of his demise.

"The United States has not yet been able to independently verify these reports and continues to monitor the situation," a spokesperson for the White House National Security Council told VOA Friday, when asked about the fate of longtime Boko Haram leader Abubakar Shekau.

Reports that Shekau was dead first appeared on social media earlier this week, saying that he died during a confrontation with fighters from the rival Islamic State-West Africa terror group in northeast Nigeria's Sambisa Forest, known to be Shekau's base of operations. 

A poster advertising for the search of Boko Haram leader Abubakar Shekau is pasted on a wall in Baga village on the outskirts of Maiduguri, in the north-eastern state of Borno, Nigeria, May 13, 2013.

Some of the accounts said Shekau killed himself, either by shooting himself or by detonating a suicide vest after he was captured and told to pledge allegiance to the IS terror group.

A Nigerian army spokesman told media Friday that the military was investigating the reports, but many officials and analysts have been wary, citing the number of times Shekau has been reported killed, only to be alive days later.

A U.S. State Department spokesperson said separately it was also working to confirm the reports, noting that if true, "the death of one of the most violent terrorists in African history would be a positive development."

But the official cautioned that Shekau's death alone would not be reason to rejoice.

"Even if Shekau has been killed, terrorism remains a threat to peace and stability in the region," the spokesperson told VOA. "Boko Haram is not the only terrorist group operating in the area."

Shekau has led Boko Haram since 2009 and is blamed for orchestrating a campaign of terror that has killed more than 30,000 people and forced millions more to flee their homes. Under Shekau's leadership, the group gained additional notoriety for the 2014 kidnapping of about 300 schoolgirls from Chibok, Nigeria.

The U.S. named Shekau a Specially Designated Global Terrorist in 2012 and has been offering a reward of up to $7 million for information leading to his capture.

But despite being the target of multiple counterterrorism operations, Shekau has remained elusive, and according to the recent intelligence assessments, still commands an estimated 1,500 to 2,000 fighters across Nigeria and Cameroon.

However, Boko Haram has increasingly been challenged by IS-West Africa. The group was formed by fighters who split off from Shekau about five years ago, and has an estimated 3,500 fighters in Nigeria and surrounding countries.

Intelligence supplied to the United Nations from member states warned that IS-West Africa has recently strengthened its relationship with IS leadership in Iraq and Syria.

There have also been indications that IS-West Africa has been trying to supplant Boko Haram.

"ISWA had been making a play to expand into the Sambisa Forest, Shekau's base," Emily Estelle, a research manager with the American Enterprise Institute's Critical Threats Project, told VOA, using an acronym for IS-West Africa.

"This means that ISWA had reached a point where it felt strong enough to finally subordinate the Shekau branch," she said.