A Washington-based activist group says China is holding at least 10 children from a group of Tibetans who were fired on by Chinese security forces near the Tibetan border with Nepal last month.

In a statement issued Tuesday, the International Campaign for Tibet quotes a British mountain climber and several other witnesses who say they saw Chinese forces shoot at a group of about 70 Tibetans on Mount Cho Oyu September 30. The Tibetans are said to have been trying to flee into Nepal.

The witnesses say a 25-year-old Tibetan nun was shot and killed in the incident. They say that a short time later, three soldiers marched a group of children, ages 6 to 10, into a nearby base camp.

The campaign says at least 40 mountain climbers witnessed the incident. Witnesses say it took place about 20 kilometers west of Mount Everest near the border between Tibet and Nepal.

There has been no official comment from China about the alleged incident.

Some information for this report was provided by Reuters.