Fighters belonging to the Islamist group Boko Haram are engaged in fierce fighting with the Nigerian military, after launching an attack on the key city of Maiduguri in the north east of the country, according to reports.

"Troops are repelling a simultaneous attack on Monguno and Maiduguri by terrorists," the country's Defense Headquarters announced on Twitter.

Nigerian authorities added that a curfew was in effect in the city, and that coordinated air and ground operations were being launched to tackle the threat.

Maiduguri is home to tens of thousands of people who have fled from Boko Haram attacks elsewhere, and was recently visited by Nigeria's president, Goodluck Jonathan, according to the BBC.

Residents said that militants first attacked on the outskirts of the city around 5 a.m. Local time (11 p.m. Saturday EST), but met with resistance from troops stationed in the area, according to AFP.

Reports from Nigerian media outlets and social media suggest that, in addition to regular military forces, civilian volunteers are also engaged in the battle against the militants.

Civilian volunteers jumping into any vehicle that comes passing by and shouting "Sai dai Jonathan ya kashe mu". pic.twitter.com/Q8Vjqta5WE â€” AS Aruwa (@MusadiqZ) January 25, 2015

Nigeria's Premium Times added that members of the country's Civilian-JTF, or Joint Task Force was joining the fight. The force has been used on the front lines in the battle against Boko Haram in the country before, according to Voice of America.

A resident, Rachel Adamu, who lives around Njimtilo told Reuters "please pray for us, we are in danger, under serious attack now."

Boko Haram, which means “Western education is forbidden,” have been waging an insurgency to establish an Islamic state in northern Nigeria since 2009.