Volcán de Fuego - Spanish for Fire Volcano - is one of Central America's most active volcanoes.
The volcano spewed black smoke and ash into the sky, prompting the evacuation of some 100 people and forcing the capital's La Aurora worldwide airport to shut down its only runway.
More than 20 people have been injured.
Authorities said at least six people were dead or missing following the eruption.
National Disaster Coordinator Sergio Cabanas says an undetermined number of people also are missing following Sunday's eruption of the Volcan del Fuego, which is 44 kilometers (27 miles) from Guatemala City.More news: Giuliani: Trump team would try to avert subpoena
Guatemalan President Jimmy Morales said he would issue a declaration of a state of emergency to be approved by Congress and urged people to heed warnings from emergency officials.
"It's a river of lava that overflowed its banks and affected the El Rodeo village".
A man cleans ashes from the Volcan de Fuego off his auto in Antigua Guatemala, Sacatepequez department, southwest of Guatemala City on Sun., June 3, 2018.
Mr Cabanas said four people died when lava set a house on fire and two children perished while standing on a bridge watching the eruption.
David de Leon, a CONRED spokesman, said a change in wind was to blame for the volcanic ash falling on parts of the capital.More news: Floridians preparing for upcoming hurricane season
It is the second time that the volcano has erupted this year.
The volcano is located some 25 miles (40 km) southwest of the capital Guatemala City and is close to the colonial city of Antigua, popular with tourists and known for its coffee plantations.
The runway was closed due to the presence of volcanic ash, Guatemala's civil aviation authority said in a tweet.
The conical Volcan de Fuego reaches an altitude of 3,763 meters above sea level at its peak.More news: Microsoft is Planning to buy GitHub at $2 Billion