A second volcano erupted Saturday near the eastern DR Congo city of Goma, a week after Mount Nyiragongo roared back into life, causing devastation and sparking an exodus.
"Today the Murara volcano near an uninhabited area of Virunga erupted," government spokesman Patrick Muyaya said, referring to a wildlife reserve that is home to a quarter of the world's population of critically endangered mountain gorillas.
The eastern DR Congo city of Goma was eerily deserted after nearly 400,000 of its inhabitants fled following warnings that nearby Mount Nyiragongo volcano may erupt again.
The authorities geared up for a major humanitarian effort, centered on Sake, around 25 kilometers west of the city, where tens of thousands of people are gathered.
Located on the shore of Lake Kivu in the shadow of Africa's most active volcano, the city has lived in fear since Nyiragongo roared back into life last weekend.
The strato-volcano spewed rivers of lava that claimed nearly three dozen lives and destroyed the homes of some 20,000 people before the eruption stopped.
Scientists have since recorded hundreds of aftershocks.
They warn of a potentially catastrophic scenario -- a "limnic eruption" that could smother the area with suffocating carbon dioxide.
A report on an emergency meeting early Friday said 80,000 households -- around 400,000 inhabitants -- had emptied on Thursday following a "preventative" evacuation order.
Most people have headed for Sake or the Rwandan border in the northeast, while others have fled by boat across Lake Kivu.
Late Friday, Rwandan President Paul Kagame said those fleeing needed "urgent, global support".
Aid efforts are being organized to provide drinking water, food and other supplies, and workers are helping to reunite children who became separated from their families.
Nearly 10,000 people are taking refuge in Bukavu on the southern bank of Lake Kivu, according to Governor Theo Ngwabidje, many of them in host families.
Several days of aftershocks, some of them equivalent to small earthquakes, yielded to a quieter night Thursday, and tremors eased both in numbers and intensity, an AFP journalist said.
But late Friday afternoon black smoke could be seen rising from the crater on the horizon, causing worry.
General Constant Ndima, the military governor of North Kivu province, ordered the evacuation of districts that potentially applies to nearly 400,000 out of Goma's 600,000 residents, according to an estimate by the UN humanitarian agency OCHA.
The wider Goma area has a population of around two million.
The authorities arranged transport towards Sake, but the roads became choked with cars, trucks, buses and people seeking safety on foot.
Many spent the night in the open or slept in schools or churches.
Evacuee Eugene Kubugoo said the water was giving children diarrhea, adding: "We don't have anything to eat or any place to sleep."
Tens of thousands had fled Goma last Saturday night but many returned when the eruption ended the following day.
Friday's report, issued after experts carried out a risk assessment at the volcano's summit, said "seismicity and ground deformation continues to indicate the presence of magma under the Goma area, with an extension under Lake Kivu."
People should remain vigilant and listen to news bulletins, as the situation "may change quickly", it warned.
Volcanologists say the worst-case scenario is of an eruption under the lake.
This could release hundreds of thousands of tons of carbon dioxide (CO2) that are currently dissolved in the water's depths.
The gas would rise to the surface of the lake, forming an invisible cloud that would linger at ground level and displace oxygen, asphyxiating life.
In 1986, one of these so-called limnic eruptions killed more than 1,700 people and thousands of cattle at Lake Nyos in western Cameroon.
On Friday, almost all the shops and banks in central Goma were closed, and just a handful of people and some motorcycle taxis were on the usually bustling streets.
In the poorer districts in the north of the city, a handful of stores were open and there were more people, including children who gamboled near a water truck.
"I will stay in the city. I know that I'm in imminent danger, but I don't have a choice," said Aline Uramahoro, who has a beer store.
"I will leave when the volcano starts spitting."
Nearly 3,500 meters high, Nyiragongo straddles the East African Rift tectonic divide.
Its last major eruption, in 2002, claimed around 100 lives and the deadliest eruption on record killed more than 600 people in 1977.
Herman Paluku, who gave his age as 94, said he had seen them all -- and insisted he wouldn't budge this time.
"There is a small hill near here which means that the lava does not reach us. And that's what protects us a bit," he said in Swahili, his hands sweeping the air.
"I can never leave here, in this situation. I can't."