Three baby mountain gorillas and an adult female have died in Rwanda's Volcanoes National Park, possibly from a combination of extremely cold and rainy weather, wildlife authorities said Wednesday.
Around 680 mountain gorillas remain in the wild, making them one of the world's most endangered great apes, the World Wildlife Fund (WWF) said in a statement.
The cause of death is not yet known but there was no indication of foul play, the statement added.
"We are all shocked and saddened by the death of these baby gorillas as well as the adult female, and by the grave implications for the mountain gorilla population as a whole," Eugene Rutagarama, director of the International Gorilla Conservation Program (IGCP), said in the statement.
Around half the mountain gorilla population live in the Virunga chain of volcanoes, which straddle the central African countries of Rwanda, Uganda and eastern Democratic Republic of Congo.
The rest live in Bwindi Impenetrable Park in Uganda.
The primates are under threat from poachers, the destruction of their habitat, the live ape trade, disease and fragmentation, the WWF said.
Rwanda's gorilla-viewing tourism industry is a leading source of foreign exchange.