No evacuation order was given by authorities, and there was no immediate word on any casualties. Witnesses, though, said lava already had engulfed one highway that connects Goma with the city of Beni in North Kivu province. 

Mount Nyiragongo's last eruption, in 2002, left hundreds dead and coated airport runways in lava. 

The UN peacekeeping mission known as MONUSCO tweeted dramatic footage of the city alit, saying it was conducting reconnaissance flights over the city where it maintains a large base. 

“The lava doesn't seem to be headed toward the city of Goma. We remain on alert,” it said. 

But that did not stop thousands from fleeing, many on foot, toward the border with Rwanda just beyond the city. Car horns honked and motorcycle taxis weaved as people attempted to escape in panic. 

Others fled to Mount Goma, the highest point in the metropolitan area. Dorcas Mbulayi left her home about an hour after the volcano first showed signs of erupting. 

“We were eating when a friend of dad's called him on the phone and told him to go and look outside,” said Mbulayi, who was still a child the last time the volcano erupted. 

"Dad told us that the volcano was erupting and that we were going to go to Mount Goma to escape the lava of the volcano.” 

She also blamed authorities “for not informing us in time about the possible volcanic eruption.” 

The lack of immediate announcements from authorities and conflicting accounts circulating on social media only added to the sense of chaos in Goma. 

Authorities at the Goma Volcano Observatory initially said it was the nearby Nyamulagira volcano that had erupted. The two volcanos are located about 13 kilometers (8.1 miles) apart. 

Volcanologist Charles Balagizi said the observatory's report was based on the direction in which the lava appeared to be flowing, which was toward Rwanda rather than Goma. 

Goma sits along the border between Congo and neighbouring Rwanda, and is a regional hub for many humanitarian agencies in the region, as well as the UN peacekeeping mission known as MONUSCO. 

The volcano erupting is also close the Virunga National Park, home to some of the last mountain gorillas in the world. While Goma is home to many UN peacekeepers and aid workers, much of the surrounding eastern Congo is also under threat from a myriad of armed groups vying for control of the region's mineral resources.