A fiery volcanic eruption in Guatemala sent lava flowing into rural communities, killing at least 25 as rescuers struggled to reach people where homes and roads were charred and blanketed with ash.

The number of dead rose late on Sunday with 18 bodies found in the community of San Miguel Los Lotes, disaster agency spokesman David de Leon said, adding to the seven victims previously confirmed elsewhere earlier in the day.

At least 20 people were injured, and authorities have said they feared the death toll could rise with an undetermined number of people unaccounted for.

The Volcan de Fuego, or "Volcano of Fire," exploded in a hail of ash and molten rock shortly before noon (1800GMT), blanketing nearby villages in heavy ash. Lava began flowing down the mountain's flank and across homes and roads around 4 p.m. (2200 GMT).

Eddy Sanchez, director of the country's seismology and volcanology institute, said the flows reached temperatures of about 1,300 degrees Fahrenheit (700 Celsius).

Hundreds of rescue workers, including firefighters, police and soldiers, worked to help any survivors and recover any more bodies amid the still-smoking lava.

Firefighters said they had seen some people who were trapped, but roads were cut by pyroclastic flows and they had been unable to reach them.

Amid darkness and rain, the rescue effort was suspended until early Monday morning, municipal firefighters' spokesman Cecilio Chacaj said.