Six French missionary staff and two Nigerien guides were killed while visiting a wildlife sanctuary by as yet unidentified gunmen in the eastern part of the Niger capital Sunday, officials of France and Niger said.

The motorcycle-riding assailants shot at the visiting group in a giraffe reserve, Tidjani Ibrahim Katiella, the Tillaberi region governor, told Reuters. Authorities intercepted and killed the attackers, he said.

French President Emmanuel Macron conveyed his condolences and support for the families of the victims. Macron spoke with Niger President Mahamadou Issoufou by telephone late Sunday and both leaders said that they will use all means to determine the motive behind the shooting.

Niger Defense Minister Issoufou Katambe told Reuters that the six were staff of an international aid organization. They had earlier been incorrectly identified as tourists. A representative for the France humanitarian support group ACTED said some of the victims were staff members.

Empty magazine cartridges were found at the scene, according to an Agence France-Presse report quoting sources. Authorities said the identity of the attackers couldn't be immediately verified.

Attackers connected with Islamic State killed four U.S. troopers and five Niger nationals at the park in 2017.

The Koure region of Niger has been a safe haven from animal predators and human hunters for a tiny herd of Niger or West African giraffes for two decades. Today the animals are a significant tourist attraction. They are protected by locals and conservation groups.

France and other countries have warned against visiting areas in Niger where armed groups like Boko Haram and allies of ISIS operate. No one has claimed responsibility for Sunday's attack. Sahel groups like Islamic State in the Greater Sahara have made Tillaberi region their hideout.