The recent most violent volcano eruption in more than a century has killed at least 25 people in Guatemala.

The Fuego volcano, about 40km (25 miles) south-west of the capital Guatemala City, spewed rock, gas and ash into the sky on Sunday.

Fast-moving flows hit villages, killing people inside their homes. Hundreds were injured and many are missing. The country's main airport is closed.

President Jimmy Morales has declared three days of national mourning.

In a statement issued late on Sunday, he spoke of the nation's "deep pain" caused by the "irreparable losses" in human lives.

It was the volcano's second eruption this year. A British man who climbed a neighbouring peak the day before the eruption said he feels "fortunate" to have escaped harm.

"It's a river of lava that overflowed its banks and affected the El Rodeo village. There are injured, burned and dead people," Sergio Cabanas, the general secretary of Guatemala's CONRED national disaster management agency, said on radio.

CONRED said the number of dead had risen to 25, from an earlier estimate of seven, including a CONRED employee. 

About 3,100 people have been evacuated from the area.