The Mount Nyiragongo volcano burst into activity Saturday, spewing red fumes into the night sky, said an AFP reporter in the nearby Democratic Republic of Congo city of Goma.
Power was cut in the city and some residents began leaving their homes and heading towards the nearby border with Rwanda.
“The sky has turned red,” one resident, Carine Mbala, told AFP by telephone.
“There is a smell of sulphur. In the distance you can see giant flames coming out of the mountain.
“But there has not been any earthquake,” she added.
“People are leaving or preparing to leave,” another resident told AFP, as the streets began filling up, some carrying as much of their belongings as they could.
For the moment, there is no sign of a flow of lava from the city, the correspondent said.
Goma sits on the mountain’s southern flank and overlooks Lake Kivu.
The last time Nyiragongo erupted was January 17, 2002, killing more than a hundred people and covering almost all of the eastern part of Goma with lava, including half of the airport’s landing strip.
Hundreds of thousands fled the city.
The deadliest eruption of the 3,000-metre high volcano was in 1977, when more than 600 died.
The Goma region, which lies in North Kivu province, bordering Rwanda and Uganda, has six volcanoes, all higher than 3,000 metres.