A military source who spoke with SaharaReporters on Sunday said the town was currently under siege of the terrorists.
Mainok is about 45 km away from Maiduguri, the Borno State capital and located in the Konduga Local Government Area.
The latest attack is coming a few days after the insurgents attacked Geidam, the headquarters of Geidam Local Government Area of Yobe state and hometown of the acting Inspector-General of the Police, Baba Alkali.
Boko Haram and its offshoot, Islamic State West Africa Province, have killed thousands and displaced millions in northeastern Nigeria.
The Nigerian military has repeatedly claimed that the insurgency has been largely defeated and it frequently underplays any losses.
In the past months, soldiers have been targeted by the insurgents.
Hundreds of soldiers and officers have been reportedly killed since January 2021.
At least 33 soldiers were recently killed when two explosive-laden vehicles rammed into a military convoy in Wulgo.
The suicide bombers were identified as Abu Bakr al-Siddiq and Bana Jundullah. The group also claimed four military vehicles were destroyed.
In February, about 20 soldiers were also killed in Malari, Borno State by the insurgents.
SaharaReporters gathered that the soldiers were on patrol to clear some Boko Haram elements in the area following a credible intelligence when they were ambushed by the group.