People grabbed mattresses and other belongings and fled toward the frontier with neighboring Rwanda as a red glow filled the sky above the city and power was cut.
Dario Tedesco, a volcanologist in the lakeside city of around 2 million, told Reuters Goma did not appear to be at risk, and lava appeared to be flowing east in the direction of the Rwandan border. Earlier he had said he thought lava might hit Goma, but he later said this was not the case.
Goma sits on the mountain's southern flank and overlooks Lake Kivu.
"The sky has turned red," one resident, Carine Mbala, told Agence France-Presse (AFP) by telephone.
Volcano watchers have been worried that the volcanic activity observed in the last five years mirrors that in the years preceding eruptions in 1977 and 2002.
The Goma region, which lies in North Kivu province, bordering Rwanda and Uganda, has six volcanoes, all higher than 3,000 meters (984 feet).
