The primate was five months old when he was discovered at Istanbul airport in a wooden crate just before Christmas en route from Nigeria to Thailand and taken in a zoo in the hills outside Istanbul to recover.

Nigeria sought his repatriation and Turkey's conservation authorities launched the process but halted it after a DNA test confirmed Zeytin belonged to a species not native to Nigeria.

On Friday, Turkish officials announced that Zeytin would not be repatriated to Nigeria but kept in a zoo in Turkey.

Pandrillus Foundation in Nigeria was preparing to house Zeytin with another young gorilla of the same sub-species before sending the pair to a sanctuary in central Africa.

"We are exceedingly disappointed. There is no logic in what the Turkish government is doing," Pandrillus Foundation director Liza Gadsby told AFP.

"And if Turkey doesn't want to send him to Nigeria, but directly to a gorilla sanctuary, that's fine. But they need to do the right thing for this animal," she said.

"They did the right thing by confiscating him in the first place," but keeping him in Turkey "goes against everything that they're supposed to be doing as a signatory to CITES", or the Convention on International Trade in Endangered Species of Wild Fauna and Flora, she said.

The Pandrillus Foundation has another gorilla which was confiscated by Nigerian customs over two years ago.

Gadsby said it would begin a process on Monday to repatriate the other gorilla to a habitat country.

"We never intended to keep her," she said.