At least 25 people, many of them schoolchildren and teenagers, have died after a bus plunged into a ravine on Fogo, a Cape Verde island in the Atlantic Ocean off the coast of West Africa.

The crash occurred on a mountain road in northern Fogo late on Saturday, when the bus veered off the road and plunged about 30 metres into a steep ravine, national news agency Inforpress reported on Sunday.

Many of those on board were primary and secondary school students, the agency said.

Several injured passengers were taken to Sao Francisco de Assis Regional Hospital on Fogo.

Know the news with the 7NEWS app: Download today

Education officials said the outing was not organised by local schools but was an annual trip privately arranged by the driver, who was among those killed.