The sweeping offensive is taking place along the Niger-Nigeria border, sources said, effectively opening a new front in the fight against the Islamist terror group.
This comes a day after Boko Haram pledged allegiance to ISIS in an audio message purported to be from leader Abubakar Shekau.
Latest developments in the fight against ISIS
"Early this morning, troops from Niger and Chad launched ground and air raids against Boko Haram into Nigeria, and the operation is still continuing," said a military official in the border town of Diffa, Niger.
"It is an intensive operation that is aimed at pulverizing Boko Haram and crippling their capability," according to the source. He spoke on condition of anonymity because he is not authorized to comment publicly about the operation.
Residents said artillery fire and fighter jets pushed Boko Haram fighters into the Damasak district of Nigeria, which is a Boko Haram enclave.
"Around 6 a.m., soldiers from Niger and Chad in huge numbers confronted Boko Haram around the Doutchi area outside Diffa and later crossed the bridge into Nigeria," said Diffa resident Ari Boubakarna.
"We heard huge explosions from artillery fire and fighter jets, but the explosions receded as the troops moved further into Nigeria," Boubakarna continued.
A journalist working in Diffa saw troops headed toward the border with Nigeria, where Boko Haram fighters had taken up positions.
"They left in a huge convoy of over 200 vehicles, some of them fitted with machine guns, including armored tanks, ambulances, water tankers and cargo trucks, which indicate they were going for a prolonged operation," the journalist said.
Residents lined up the streets to offer water and tea as the troops drove out of Diffa, residents said, adding that soldiers promised to capture Shekau alive.
Another contingent of troops, backed by air support, moved out from the town of Bosso, Niger, according to residents.
"Soldiers in large numbers crossed into Nigeria this morning, and we could hear thunderous sounds of gunfire and explosions coming from the direction of Malam Fatori," Bosso resident Tandja Moumouni said.
Nigeria and its neighbors have recently mounted a coordinated offensive against Boko Haram militants in the Borno state, where the Islamist group has seized a large swathe of territory. Nigeria shares a border with Niger, Chad and Cameroon there.
As a part of this alliance, thousands of troops from Niger and Chad were stationed in Bosso and Diffa in January.
The offensive has succeeded in reclaiming some of the territory seized by the group.
Nigeria has vowed to liberate all of its territories from Boko Haram before the general elections, which begin on March 28, to enable displaced residents return to their homes for the elections.