The armies of Chad and Niger have launched a joint offensive against the Nigeria-based Islamist group Boko Haram.
Military sources said Chadian and Nigerian forces began the offensive Sunday morning in Nigeria's northeastern Borno state.
Sunday's strike marks Niger's first incursion deep into Nigerian territory; the country's troops had until now only fought Boko Haram in the border area.
Chad has already sent troops many kilometers inside northeastern Nigeria, winning back areas from the Sunni jihadist group near the Nigeria-Cameroon border.
"We can confirm that Chadian and Nigerien forces launched an offensive this morning from Niger. The offensive is underway," Colonel Azem Bermandoa, a spokesman for Chad's army, told Reuters.
A witness in Niger's southeastern town of Diffa told Reuters he saw a convoy of at least 300 vehicles, including army jeeps equipped with heavy weapons as well as water and fuel trucks, leaving barracks overnight and heading to the border.
The two nations join Cameroon and Nigerian in the fight against the group that recently pledged allegiance to the Islamic State group.
Boko Haram, IS allegiance
On Saturday, Jihadist monitoring group SITE quoted Boko Haram as saying, "We announce our allegiance to the Caliph" in a video purporting to be from the Nigerian rebel group.
The voice purportedly of Boko Haram leader Abubakar Shekau said the group "will hear and obey" Islamic State leader Abu Bakr al-Baghdadi "in times of difficulty and prosperity, in hardship and ease. ..."
Islamic State militants control parts of Iraq and Syria and call its leader the caliph. Both the Islamic State group and Nigerian-based Boko Haram follow the strictest interpretation of the Quran and are responsible for thousands of deaths.
Still, U.S. intelligence officials remained skeptical that Boko Haram and the Islamic State group had forged any “deep operational partnership."
A U.S. intelligence official, speaking on condition of anonymity, told VOA on Saturday that even if the new pledge was authentic, it was unlikely to change the way either group operates.
“It’s probably more for propaganda purposes than anything else,” the official said, noting Boko Haram had previously pledged allegiance to both core al-Qaida and al-Qaida in the Islamic Maghreb, only to “blatantly” disregard subsequent guidance from both groups.
However, the official did not rule out the role money might have played in Boko Haram’s decision-making.
“Boko would not turn down any funding or material support; they are takers who give little in return,” the official said.
Daveed Gartenstein-Ross, a senior fellow at the Foundation for Defense of Democracies, agreed that if the pledge was real, Boko Haram most likely had some extra motivation.
“There is almost certainly money involved in the deal,” he said.
There has been some evidence that despite a decline in revenues, the Islamic State group has been throwing money around in hopes of countering losses on the ground in Iraq.
“Islamic State has been trying to show that it has momentum by luring more affiliates,” Gartenstein-Ross said. “They have a business model that requires them to maintain the perception of momentum.”
Saturday's announcement came hours after explosions in the Borno State capital Maiduguri killed at least 55 people, and wounded about 140 others.
Four blasts struck the town within hours, some of them detonated by female suicide bombers, police said. One blast from a suicide bomber on a rickshaw hit a busy fish market. Another bomb went off at a different market, known as the Monday Market.
A VOA reporter said a group of young vigilantes had barricaded major roadways, detouring traffic and causing panic. He said several of the vigilantes stopped one of the bombers from reaching the center of the market, but lost their lives when the bomber detonated.
On Friday, reports from Nigeria said members of Boko Haram were gathering in their stronghold of Gwoza and bringing in reinforcements from other locations.
An intelligence source who is monitoring the situation told VOA that military forces are getting closer to the town and the militants may be preparing to defend Gwoza, which is one of the last major towns they control in northeastern Nigeria.
The source says Boko Haram reinforcements are traveling to Gwoza from their refuge in the nearby Sambisa forest.
Gwoza is located about 135 kilometers south of Maiduguri.
Jeff Seldin contributed to this report. Some material for this report came from Reuters.