MANAGUA (AFP) - The San Cristobal volcano, the highest in Nicaragua and one of its most active, spewed a cloud of ash Tuesday (March 9) that blanketed the city of Chinandega and surrounding communities, a local journalist told AFP.

The surprise eruption ejected a column of smoke and ash that was dumped as far as 17km from the volcano's foot, Nicaragua journalist Carol Altamirano said.

The Ineter territorial studies institute has not issued a report on the eruption, but the non-governmental organisation Humboldt reported four explosions.

"Everything is grey, the crops of rice, sesame, vegetable gardens and fruit trees and the cattle pasture is covered in ash," said Altamirano.

The massive ash deposit lasted about 30 minutes, and deep rumbling from the volcano alarmed locals, she added. Cars switched on their headlights as everything went dark.

Farmers in the area covered their water sources and moved their animals to safe places, while in the city people used umbrellas, caps and face masks to shield themselves from the ash rain, said the journalist.

The 1,745-metre high San Cristobal is one of seven active volcanoes in the Central American country.

It is located in the Chinandega region, 132km northwest of the capital Managua.