The risk of further eruptions from the Nyiragongo volcano has led authorities in the Democratic Republic of the Congo to order the evacuation of parts of Goma, causing an exodus of tens of thousands of people from the city.

“Current data on seismicity and the deformation of the ground indicate the presence of magma under the urban area of Goma, with an extension under Lake Kivu,” the local military governor, Gen Constant Ndima, said in a public address.

“We can’t rule out an eruption on land or under the lake, which could happen very soon and without warning. The situation can change rapidly, and is being constantly monitored.”

Ndima said there were additional risks associated with the interaction between magma and water in Lake Kivu.

There were several potential problems linked to this, he explained, among them the “destabilisation of the volume of gas dissolved in Lake Kivu and the emission of potentially dangerous gases at the surface”.

Residents carry belongings as they escape Goma.
Residents carry belongings as they escape Goma. Photograph: Moses Sawasawa/AP

He said evacuation was necessary and should be done calmly.

Authorities have arranged transport towards Sake, about 12 miles (20km) west of Goma, in each of the 10 districts of the city affected, Ndima said. “People should take the bare minimum with them, to make sure everyone has a chance to get on.”

The announcement was followed by the immediate departure of tens of thousands of people towards the south-west, in the direction of the Rwandan border.

The UN says 32 people have died and at least 5,000 are feared to be homeless after the volcano erupted on Saturday.

DR Congo volcano: thousands flee as Mount Nyiragongo lava flows destroy homes – video
DR Congo volcano: thousands flee as Mount Nyiragongo lava flows destroy homes – video

The UN humanitarian affairs office, Ocha, said 24 of the victims were killed by lava and 40 adults had been reported missing.

By the time the eruption ended on Sunday the volcano had spewed out two rivers of molten rock, one of which came to halt on the edge of Goma after obliterating villages in its wake.

Goma, a lakeshore city of 1.5 million people, is about eight miles from the volcano.

Local volcanologists have recorded hundreds of aftershocks since Nyiragongo roared back to life, including 119 on Monday alone.

Known as a stratovolcano, Nyiragongo is nearly 3,500 metres (11,500ft) high and straddles the east African Rift tectonic divide. The previous big eruption, in 2002, killed about 100 people.