(CNN) -- The shooting deaths of four mountain gorillas -- three females and an alpha male silverback -- are prompting a United Nations agency to send a mission to the Democratic Republic of Congo.
Park rangers found the three females and an alpha male silverback earlier this week.
Rangers made the gruesome find in the southern sector of Virunga National Park earlier this week, said Flora and Fauna International, an organization that acts to conserve threatened species and ecosystems. The group said it is unclear who shot the gorillas or why.
"Just over 700 mountain gorillas survive in the wild today, and none exist in captivity," Flora and Fauna International said in a statement. "For such a small population, the unnecessary and indiscriminate killing of four mountain gorillas is a huge loss."
The U.N. Educational, Scientific and Cultural Organization (UNESCO) said Friday it will send a mission to the site as soon as possible "to provide support to those fighting to preserve the integrity of Virunga National Park."
The agency said it will try to find out the reasons behind the slayings and work with Congolese authorities and the Congolese Institute for Nature Conservation to prevent future deaths.
The females, named Safari, Neeza and Mburanumwe, and the male, Rugendo, were shot Sunday night, UNESCO said. They belonged to a group that was frequently visited by tourists, providing an economic boon to the area. "The situation threatens to become an ecological and economic disaster for the neighboring local communities," the agency said in a statement.
The chief executive of Flora and Fauna International expressed deep concern about the killings, which he said follow more than 20 years of successful collaboration for mountain gorilla conservation.
"Whatever the motive underlying this tragedy, the gorillas are helpless pawns in a feud between individuals," Mark Rose said.
The death of Rugendo could have a ripple effect, the organization said. "Alpha males fulfill a leadership role within a group, and in their absence the integrity of the group is often compromised."
Rugendo's group contained 12 gorillas before he was killed, the group said. Now, six have been found safe, but two -- a female and an infant -- are missing.
Seven gorillas have been killed in the park so far this year, Flora and Fauna International said.
At least two of them were believed killed by supporters of rebel leader Gen. Laurent Nkunda, Flora and Fauna International said. The skin of one was found in a latrine in a nearby rebel camp. The infant of another female gorilla is being hand-raised by the nature conservation institute, which oversees the Democratic Republic of Congo's wildlife and protected areas.
Nkunda's rebels have been fighting government troops in the eastern part of the country for several years.
Conservation institute patrols were increased in the park's southern sector with support from the DRC army, the organization said, and guard posts are being built to enable 24-hour park surveillance.
The bodies of the four gorillas will undergo post-mortem examinations, Flora and Fauna International said, and will be buried near Bukima, a park outpost.
"Just two months ago, we celebrated the increase of the gorilla population in Bwindi Impenetrable National Park in Uganda," said Kwame Koranteng, a regional representative of the World Wildlife Fund's Eastern Africa Regional Program Office, in the Flora and Fauna statement. "Seven gorillas killed in seven months is a horrifying statistic and a trend that cannot continue." E-mail to a friend