"It's a river of lava that overflowed its banks and affected the Rodeo village".
The volcano, about 40km south-west of the capital Guatemala City, has been spewing black smoke and ash into the sky.
The Volcan de Fuego in Guatemala has erupted, shooting ash 10 km into the air and blanketing villages within 25km of the crater. "There are injured, burned and dead people", Sergio Cabanas, the general secretary of Guatemala's Conred disaster agency, said on radio, according to the Guardian.
People have been evacuated from several areas and the capital's La Aurora airport has closed.
One video published by news outlet Telediario purportedly taken in the El Rodeo village showed three bodies strewn atop a lava flow, as rescuers arrived to attend to an elderly man caked from head to toe in ash and mud.
Officials said the dead were so far all concentrated in three towns: El Rodeo, Alotenango and San Miguel los Lotes. Lesser amounts of ash reached the capital of Guatemala City some 25 miles away, forcing the closure of its global airport, CONRED said.
The conical Volcan de Fuego reaches an altitude of 12,346ft (3,763 meters) above sea level at its peak.
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An employee sweeps the entrance of a gas station covered with ash after Guatemala's Fuego volcano erupted violently, in Guatemala City, Guatemala June 3, 2018.
Photos shared on social media show huge plumes of smoke rising into the sky.
Explosions are still coming from the volcano, said Eddy Sánchez, director of the National Institute for Seismology, Vulcanology, Meteorology and Hydrology of Guatemala known as INSIVUMEH.
The dead were from farming communities just south of the volcano who were trapped by hot lava flow, National Disaster Relief Agency spokesman David de Leon told reporters.
The river of lava has reportedly changed direction and is now heading toward a small town.
Residents have been urged to wear masks due to the falling ash.
It is the second time the volcano has erupted this year, setting off loud explosions and spewing ash almost four miles into the sky.