Five people were found choked to death on toxic fumes from the eruption of eastern DR Congo’s Nyiragongo volcano on Monday, as strong aftershocks rocked the city of Goma.

The deaths bring to 20 the number killed since Africa’s most active volcano erupted on Saturday, spewing red-hot molten lava that engulfed houses in its wake.

“We have just discovered five dead people,” civil society leader Mambo Kawaya told AFP, saying that they were “asphyxiated by the gas” as they tried to cross the cooling lava some 13 kilometres (eight miles) north of Goma.

A sixth person is in a “critical state with trouble breathing and has been taken to hospital,” Kawaya said.

Goma, a city of some 1.5 million people in the shadow of the volcano, was on edge as violent aftershocks continued through the night and into Monday morning.

“They’re multiplying and they come at any moment,” one resident told AFP, describing the aftershocks as “very worrying”.

“The night was long — there is fear in our stomachs,” she said.

Tens of thousands of residents had fled the city in panic — around 7,000 of them to neighbouring Rwanda — when Nyiragongo began erupting on Saturday evening.

A 4.5-magnitude quake followed at 1153 GMT, the RSM said on Twitter, adding that the tremors were being “produced by vibrations generated by the movement of magma within the volcano”.

Tens of thousands of residents had fled the city in panic—around 7,000 of them to Rwanda—when Nyiragongo began erupting on Saturday evening.

Along with the five people found dead on Monday, at least 15 other people have died, although most were not killed directly by the eruption.

Authorities said nine people died in accidents during the rush to evacuate, while four prisoners were killed while trying to escape in the melee. Two people were found burned to death.

Officials said 17 villages on the city’s fringes had suffered major damage.

Schools shut, electricity cut

While the river of lava stopped at the edge of Goma and many residents have now returned, each aftershock brought anxious residents back out onto the streets on Monday.