The Chaparrastique volcano in eastern El Salvador has belched a column of hot ash high into the air, frightening nearby residents and prompting authorities to order evacuations in the area.
Civil protection authorities said on Sunday they would evacuate people from within three kilometres of the volcano and set up emergency shelters.
"The evacuations began almost right after the explosion," said civil protection official Armando Vividor.
He said about 5,000 people live around the volcano. There were no immediate reports of injuries in the San Miguel region, where the volcano is located and that is known for its coffee plantations.
The volcano, which is about 140 kilometres to the east of the capital, spewed ash over a wide area and the smell of sulphur hung over surrounding towns, according to reports on social media.
Santos Osorio, a member of a local coffee growers union, said heavy ash was falling in the area and coffee plantations would be checked for damage.
El Salvador has 23 active volcanoes and the Chaparrastique volcano is considered one of the most active, with 26 eruptions in the last 500 years, the environment ministry said.
In a 1976 eruption, lava gushed from the volcano and it shook violently in another event in 2010.