Four rare mountain gorillas have been killed after gunmen crept up on them and opened fire in the Democratic Republic of Congo's Virunga National Park. Nick Wadhams has more on the story from Nairobi.

The gorillas were shot Sunday night. One was pregnant and another was a female named Safari, who received widespread international attention
when she gave birth in February.

Her five-month-old baby was still breast feeding and was initially feared to have died of dehydration. But rangers reported finding the baby, Ndeze, on Thursday, and took him for medical treatment.

The attacks are devastating for the gorilla population in Virunga, where some 100 of the world's 700 mountain gorillas live. At least three others have been killed in Virunga so far this year.

The director of the Nairobi-based conservation group WildlifeDirect, Emmanuel de Merode, says two others from the group of 12 gorillas were missing.

De Merode says the gorillas were probably killed by traders who cut down trees in Virunga to be sold as charcoal in Rwanda and the nearby city of Goma, which has about 500,000 people and a charcoal industry that is worth about $30 million each year. Park rangers have campaigned hard to keep charcoal traders out, infuriating them.

"In the last year there's been a huge increase in pressure on the park for timber to supply the charcoal industry both for the town of Goma which is a town of half a million inhabitants, and Rwanda," De Merode said. "So what we find is that the rangers are under a lot more pressure than they used to be because they're the ones defending the park against the destruction of the forest, and that forest is also the gorillas' habitat, and now what's happening is they're confronting huge financial interests."

The situation in Virunga has become worse recently because Rwanda has banned the production of charcoal, which is used for cooking fires. That has sent even more traders across the border and into Virunga for wood.

The gorillas have also come under pressure from armed militias that hunt the animals for their meat. The nearly 8,000 square-kilometer park is home to a handful of militias and more than 100 rangers have been killed in recent years trying to protect the wildlife.

De Merode says the rangers are the main line of defense between poachers and militias in the park.

"What is true is there's a huge determination on the part of those rangers to do their job," De Merode said. "They've remained committed to their job throughout the last 12 years of civil war in Congo. Many of those years they didn't receive their salaries, many of them died protecting the park. And so that's very much where our hopes are tied with those Congo rangers on the ground. They really are professional, and they just need support."

During Congo's civil war, the park became a hiding place for various factions. Tourism has only begun to inch back up now that the civil war is over, but officials worry that the new killings will give further reason for people to stay away.