By Helen Vesperini BBC correspondent in Kigali

Poachers in Rwanda have killed two mountain gorillas, a highly endangered species and a major tourist attraction found only in the volcanic mountains on the borders of Rwanda, Congo and Uganda.

Two men are being held in police custody over the killing of the gorillas but the Rwandan authorities are convinced they are part of a bigger criminal ring.

The Rwanda army frequently clashes with the rebels

The aim of the poachers, who attacked just before nightfall on Thursday, was to capture and sell baby gorillas.

Wildlife officials say the poachers made off with one baby after they killed two females in the least accessible of the groups of habituated animals.

This attack is the first by poachers in almost two decades here.

Last year Rwandan rebels returning from Congo broke what is a major taboo in the region when they killed two animals and roasted them to eat the meat.

Tourist draw

There are just 350 mountain gorillas left in Rwanda.

For Rwanda their presence is a stroke of good fortune as tourists flock to visit, bringing much needed dollars with them.

Gorilla tracking here entails scrambling on all fours through the mud in dense bamboo thickets at high altitudes.

Nor does it come cheap - one hour with the animals costs $250.

But tourists are never disappointed. Watching a female dangle her baby at arm's length, coo at it in admiration and then pull it close for a cuddle is an almost disturbing reminder of the links between homo sapiens and gorilla gorilla.