The volcanic eruption spewed a river of red, hot lava and belched thick clouds of smoke nearly six miles into the air, according to the CONRED, the government's national coordinator for disaster reduction.
The CONRED confirmed late Sunday that the official death toll had increased to 25.
It urged residents living near the volcano to evacuate immediately and warned residents of the states of Chimaltenango, Sacatepequez and Escuintla to watch out for volcanic rocks and ash.
The explosion stands to affect 1.7 million people, said Sergio García Cabañas, director of CONRED.
More than 3,100 people have been evacuated from their homes while search and rescue efforts continue into the night, Cabañas said.
So far, 15 been have been hospitalized, including 12 children, some of whom suffered severe burns, the Minister of Health said.
The volcano, whose name means fire, is one of Central America's most active. It is located near the colonial city of Antigua. Sunday's explosion rained soot over the popular tourist destination and other villages in the Sacatepéquez department, covering them in ash.
Villages south of the volcano in the Escuintla department were affected, too, Cabañas said. Lesser amounts of ash reached the capital of Guatemala City some 25 miles away, forcing the closure of its international airport. The Guatemalan Army shared images of officers clearing the runway with push brooms.
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.
He warned of mudslides as rainfall continues, and urged people to stay off roads close to the volcano.
Mexican President Enrique Peña Nieto expressed condolences and offered assistance.
"All our solidarity and support to the President Jimmy Morales and the Guatemalan people for the loss of human life after the eruption of the volcano of Fire."
The President of El Salvador offered his condolences via Twitter and said he his country stood ready to assist its neighbor.
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