The Rwandan government said Friday it will increase the cost of a permit to track the endangered mountain gorillas, the country's main tourist attraction, to $750 from $500 starting June 1.

"This increase comes at a time when there is significant growth of the gorilla population as well as an increasing demand for gorilla tourism," a statement from the Rwanda Development Board said.

"This means that there is need to continue channeling all our efforts in conservation in order to protect their environment as well as the rare species."

The permit allows visitors to spend around one hour observing the primates, estimated to total just 790 worldwide.

They are concentrated in the Virunga massif that straddles the border between Rwanda, DR Congo and Uganda and are also found in Uganda, in the Bwindi Impenetrable Forest.